Semiconductor light-emitting device, surface-emission laser diode, and production apparatus thereof, production method, optical module and optical telecommunication system

ABSTRACT

A semiconductor light-emitting device has a semiconductor layer containing Al between a substrate and an active layer containing nitrogen, wherein Al and oxygen are removed from a growth chamber before growing said active layer and a concentration of oxygen incorporated into said active layer together with Al is set to a level such that said semiconductor light-emitting device can perform a continuous laser oscillation at room temperature.

This application is a divisional application of U.S. patent applicationSer. No. 10/105,800, filed on Mar. 26, 2002 now Pat. No. 6,765,232, theentirety of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to the technology of opticaltelecommunication and more particularly to an optical semiconductordevice such as a laser diode used in optical telecommunication systems.Especially, the present invention is related to a surface-emission laserdiode and fabrication process thereof, a growth apparatus and a growthprocess used for forming such a surface-emission laser diode, as well asoptical transmission modules, optical transceiver modules and opticaltelecommunication systems that use such a surface-emission laser diode.

With wide spread use of Internet, there is going on some kind ofexplosion of information handled by telecommunication systems. In viewof this situation, optical fibers are now being deployed not only intrunk lines but also in subscriber lines or LANs (local area networks)located near the side of users. Further, optical fibers are introducedalso for interconnection of various apparatuses or for interconnectioninside an apparatus. Thus, the importance of large-capacity opticaltelecommunication technology is increasing evermore.

In order to realize inexpensive long-range optical telecommunicationnetworks or large-capacity optical telecommunication networks, it isadvantageous to use a vertical-cavity surface-emission laser diode(VCSEL, referred to hereinafter simply as “surface-emission laserdiode”), in which an optical cavity is provided in a directionperpendicular to the epitaxial layers constituting the laser diode. Inview of minimum optical loss of silica-based optical fibers in thewavelength band of 1.3 μm and 1.55 μm, the surface-emission layer diodefor use in such an optical telecommunication system is required tooscillate at the wavelength band of 1.3–1.55 μm. Here, the use of asurface-emission laser diode is particularly advantageous in view of itslow cost, low power consumption, compact size and easiness of forming atwo dimensional array.

There already exists a surface-emission laser diode constructed on aGaAs substrate and operable in the wavelength band of 0.85 μm. Thus,such a surface-emission laser diode is used in a high-speed LAN such as1 Gbit/s Ethernet.

In the 1.3 μm band, on the other hand, a semiconductor material of InPhas been used commonly in the conventional edge-emission type laserdiodes. On the other hand, conventional laser diode of the 1.3 μm bandthus constructed on the InP substrate has suffered from the problem oflarge increase of drive current, by the factor of three times or more,when the environmental temperature has increased from room temperatureto 80° C. Further, there has been a problem in that no satisfactorydistributed Bragg reflector could be constructed on an InP substrate,and thus, it has been difficult to construct a surface-emission on suchan InP substrate.

In view of the foregoing difficulty, there has been a proposal to bondan active structure of a surface-emission laser diode including an InPsubstrate and an active layer on a distributed Bragg reflector of anAlGaAs/GaAs stacked structure formed on a GaAs substrate (V. Jayaraman,J. C. Geske, M. H. MacDougal, F. H. Peters, T. D. Lowes, and T. T. Char,Electron. Lett., 34, (14), pp.1405–1406, 1998).

However, such a construction becomes inevitably expensive and has anobvious problem of poor efficiency of production.

In view of the foregoing problems, efforts are being made to construct asurface emission laser diode operable in the wavelength band of 1.3 μmon a GaAs substrate, by using (Ga)InAs quantum dots for the activelayer, or a compound semiconductor material such as GaAsSb or GaInNAsfor the active layer. Reference should be made to Japanese Laid-OpenPatent Publication 6-37355. Particularly, GaInNAs is expected as being asemiconductor material capable of minimizing the temperature dependenceof the laser diode.

A GaInNAs laser diode constructed on a GaAs substrate has anadvantageous feature of reduced bandgap for the active layer as a resultof incorporation of N in the active layer, and thus, the laser diodebecomes operable in the wavelength band of 1.3 μm even in the case thelaser diode is constructed on a GaAs substrate. When the In content is10%, for example, the wavelength band of 1.3 μm is realized byintroducing N into the active layer with a concentration of about 3%.

FIG. 1 shows the relationship between the threshold current density oflaser oscillation and the N content in the active layer for a laserdiode having a GaInNAs active layer, wherein the vertical axisrepresents the threshold current density while the horizontal axisrepresents the N content in terms of percent.

Referring to FIG. 1, it can be seen that there occurs a steep increasein the threshold current with the N content in the active layer, whereinit is believed that the relationship of FIG. 1 reflects the situation inwhich the degree of crystallization of the GaInNAs active layer isdeteriorated with increase of the N content in the active layer.

Thus, the growth process of high quality GaInNAs layer becomes the keyissue in the fabrication of such a surface-emission laser diode operableat the wavelength band of 1.3–1.55 μm.

Generally, a GaInNAs layer can been grown by an MOCVD (metal organicchemical vapor deposition) process or MBE (molecular beam epitaxy)process, wherein MOCVD process, in which the supply of source materialis controlled by controlling a gas flow rate of the source material, isthought more advantageous and suitable for mass production of the laserdiode as compared with MBE process, in which the supply of the sourcematerial is controlled solely by the control of the temperature ofsource cells, in view of the fact that the MOCVD process does notrequire a highly vacuum environment such as the one needed in the caseof an MBE process, and a large growth rate is achievable easily.Thereby, the throughput of device production can be increased. In fact,mass production of the surface-emission laser diodes of the 0.85 μm bandis achieved already by using an MOCVD process.

FIG. 2 shows the construction of a typical MOCVD apparatus used forgrowing group III–V semiconductor layers.

Referring to FIG. 2, the MOCVD apparatus is generally formed of a sourcegas supply system A for supplying a source gas, a susceptor B forsupporting the substrate S and an evacuation unit C such as a vacuumpump for evacuating gases that have caused a reaction.

Generally, the substrate S is first loaded in a load/unload chamber 11and is then transported to a growth chamber (reaction chamber) 12 afterevacuating the air in the load/unload chamber 11 by driving theevacuation unit C.

Typically, the growth chamber is controlled to have an internal pressureof 50–100 Torr, and one or more of the metal organic sources such as TMG(trimethyl gallium), TEG (trimethyl gallium), TMA (trimethyl aluminum),TMI (trimethyl indium), and the like, are introduced into the growthchamber 12 as the source of group III element, together with a source ofgroup V element. As a group V source, a hydride gas or organic compoundsuch as AsH₃, TBA (tertiary butyl arsine), PH₃, TBP (tertiary butylarsine), and the like is used.

These gaseous sources are transported to the growth chamber by ahydrogen carrier gas, wherein the hydrogen carrier gas is generally usedafter removing impurity by passing through a purifier 13.

For the source of nitrogen, organic compounds such as DMHy (dimethylhydrazine), MMHy (monomethyl hydrazine), and the like, are used,although there are possibilities of using other materials.

In the case of using a liquid or solid source material, the sourcematerial is held in a bubbler 14 and the vapor of the source material orsource gas formed as a result of bubbling in the bubbler 14 by thecarrier gas, is supplied. The hydride gas, on the other hand, is held ina gas cylinder 15.

In the example of FIG. 2, two bubblers #1 and #2 are provided forholding two difference source materials and two gas cylinders #1 and #2are provided for holding two different gaseous source materials.

The path of the source gases is selected according to the needs bycontrolling the valves forming a valve array 16, and the flow rate ofthe individual gases is controlled by using a mass flow controller(MFC). In such a gas supply system, it is practiced to provide dummy gaslines such as lines #1 and #2 for avoiding change of gas flow rate, gaspressure, and the like.

In an MOCVD process that is conducted by using the system such as theone shown in FIG. 1, the thickness of the semiconductor layers iscontrolled by way of controlling the duration of supply of the sourcegases. Thus, the MOCVD process provides excellent throughput and isthought most suitable for mass production of semiconductor devices.

FIG. 3 shows a typical MBE apparatus.

MBE process is a modification of the vacuum evaporation depositionprocess and uses source molecules or atoms emitted from a source cell.The source molecules or atoms thus emitted by the source cell cause adeposition on the surface of a heated substrate after traveling througha growth chamber, which is held in a high vacuum state.

Referring to FIG. 3, the MBE apparatus includes a growth chamber 21coupled with the load/unload chamber 11 similarly to the MOCVD apparatusof FIG. 2, wherein the growth chamber 21 is evacuated to a high vacuumstate by the vacuum pump 23 and the substrate S is held on a susceptor25 having a heating mechanism. The growth chamber 21 is provided withmolecular beam cells 21A and 21B for holding solid sources and also amolecular beam cell 21C of nitrogen, which is actually a nitrogenradical cell.

As no hydrogen or carbon is contained in the source in the case of theMBE process, the semiconductor layers grown on the substrate 24 containslittle impurities and high quality semiconductor layers are obtained.

On the other hand, the MBE process has a drawback in view of the need ofhigh vacuum state in that it is not possible to increase the supply rateof the source materials. When the supply rate of the source materials isincreased, the load of the evacuation system becomes excessively large,and the system would undergo frequent failure or need frequentmaintenance operations. Thus, the MBE process inherently suffers fromlow throughput.

While there are reports in these days about laser diodes, includingsurface-emission laser diodes, that use the system of GaInNAs for theactive layer, that are operable in the wavelength band of 1.2 μm (M. C.Larson, et al., IEEE Photonics Technol. Lett., 10, pp.188–190), most ofthe reports are based on the devices produced by an MBE process.

In view of the poor throughput of the MBE process noted above, andfurther in view of the fact that the GaInNAs surface-emission laserdiode thus formed by the MBE process suffers from the problem of verylarge resistance caused by the p-side distributed Bragg reflector, theinventors of the present invention have conducted a series ofexperimental investigations on the fabrication process of GaInNAs laserdiode, particularly a surface-emission laser diode that uses GaInNAsformed by an MOCVD process for the active layer and identified the causeof deterioration of the GaInNAs active layer crystal.

More specifically, the Japanese Laid-Open Patent Publication 10-126004describes the discovery made by the inventors of the present inventionin that there occurs a segregation of N at the interface between aGaInNAs active layer and an underlying Al-containing layer when theGaInNAs active layer is grown in direct contact with the underlyingAl-containing layer Al and that such a segregation of N causes asubstantial deterioration of surface morphology of the GaInNAs activelayer. Thus, in order to avoid the foregoing problem, the foregoingJapanese Laid-Open Patent Publication 10-126004 has proposed a structurein which there is provided a layer free from Al such that the Al-freelayer makes a direct contact with the GaInNAs active layer.

Further, Japanese Laid-Open Patent Publication 2000-4068 proposes astructure that provides an intermediate layer free from both Al and Nbetween the GaInNAs active layer and the AlGaInP cladding layer foravoiding the degradation of the GaInNAs active layer.

On the other hand, there is a report that there can be caused adegradation of efficiency of optical emission in the GaInNAs activelayer provided on an Al-containing semiconductor layer even in such acase in which an intermediate layer free from Al and N is interposedbetween the Al-containing semiconductor layer and the GaInNAs activelayer. For example, there is a report in Electron. Lett., 2000, 36 (21),pp.1776–1777 reports the discovery of severe degradation ofphotoluminescence intensity in a GaInNAs quantum well layer grown by anMOCVD process on an AlGaAs cladding layer continuously. In order toimprove the photoluminescence intensity, the foregoing literature thususes different MOCVD chambers for growing the AlGaAs cladding layer andthe GaInNAs active layer.

FIG. 4 shows the room-temperature photoluminescent spectrum of aGaInNAs/GaAs double quantum well structure formed by the inventor of thepresent invention by an MOCVD process, wherein it should be noted thatthe curve designated as “A” represents the case in which theGaInNAs/GaAs double quantum well structure is formed on an AlGaAscladding layer with an intervening GaAs layer, while the curvedesignated as “B” represents the case in which the GaInNAs/GaAs doublequantum well structure is formed on a GaInP cladding layer with anintervening GaAs layer.

As can be seen in FIG. 4, the photoluminescence intensity for the sampleA is less than one-half of the photoluminescent intensity for the sampleB.

The result of FIG. 4 thus shows clearly that there occurs severedegradation in the efficiency of optical emission in the GaInNAs layerin the case the GaInNAs layer is formed on a semiconductor layercontaining Al as a constituent element such as AlGaAs by using a singleMOCVD apparatus, even in the case an intervening Al-free intermediatelayer is provided. Associated with such a degradation of quality of theGaInNAs layer, the laser diode that uses such a GaInNAs layer suffersfrom the problem of poor threshold characteristics characterized by alarge threshold current, which can become twice as large as thethreshold current for the case in which the same active layer is formedon a GaInP cladding layer.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providea novel and useful light-emitting semiconductor device and fabricationprocess thereof wherein the foregoing problems are eliminated.

Another and more specific object of the present invention is to providea semiconductor light-emitting device, comprising:

-   -   a substrate;    -   an active layer containing N; and    -   a semiconductor layer containing Al interposed between said        substrate and said active layer,    -   said active layer being grown by using a nitrogen compound        source,    -   said semiconductor layer containing Al being grown by using a        metal organic source of Al,    -   said active layer containing an impurity element forming a        non-optical recombination level with a concentration level such        that said semiconductor light-emitting device can cause a        continuous laser oscillation at room temperature.

Another object of the present invention is to provide a semiconductorlight-emitting device, comprising:

-   -   a substrate;    -   an active layer containing nitrogen;    -   a semiconductor layer containing Al provided between said        substrate and said active layer,    -   said active layer being grown by using a nitrogen compound        source,    -   said semiconductor layer being grown by using a metal organic        source of Al,    -   said active layer containing oxygen with a concentration level        such that said semiconductor light-emitting device can cause a        continuous laser oscillation at room temperature.

Another object of the present invention is to provide a semiconductorlight-emitting device, comprising:

-   -   a substrate;    -   an active layer containing therein nitrogen; and    -   a semiconductor layer containing therein Al provided between        said substrate and said active layer,    -   wherein said active layer is grown by using a nitrogen compound        source, said semiconductor layer is grown by using a metal        organic source of Al, and    -   wherein said active layer contains oxygen with a concentration        level of less than 1.5×10¹⁸ cm⁻³.

Another object of the present invention is to provide a semiconductorlight-emitting device, comprising:

-   -   a substrate;    -   an active layer containing nitrogen;    -   a semiconductor layer containing Al provided between said        substrate and said active layer,    -   said active layer being grown by using a nitrogen compound        source,    -   said semiconductor layer being grown by using a metal organic        source of Al,    -   wherein said active layer contains Al with a concentration level        such that such that said semiconductor light-emitting device can        cause a continuous laser oscillation at room temperature.

Another object of the present invention is to provide a semiconductorlight-emitting device, comprising:

-   -   a substrate;    -   an active layer containing nitrogen;    -   a semiconductor layer containing Al provided between said        substrate and said active layer,    -   said active layer being grown by using a nitrogen compound        source,    -   said semiconductor layer being grown by using a metal organic        source of Al,    -   wherein said active layer contains Al with a concentration level        of less than 2×10¹⁹ cm⁻³.

Another object of the present invention is to provide method offabricating a semiconductor light-emitting device having a semiconductorlayer containing Al between a substrate and an active layer containingN, said method comprising the steps of:

-   -   growing said semiconductor layer in a growth chamber; and    -   growing said active layer in said growth chamber,    -   wherein said step of growing said active layer is conducted        inside said growth chamber without taking out said substrate to        the atmosphere after said step of growing said semiconductor        layer.

Another object of the present invention is to provide a method offabricating a semiconductor light-emitting device, said semiconductorlight-emitting device having a semiconductor layer containing Al betweena substrate and an active layer containing nitrogen, said methodcomprising the steps of:

-   -   heating a susceptor in a growth chamber;    -   growing said semiconductor layer in said growth chamber while        using a metal organic source of Al; and    -   growing said active layer in said growth chamber while using a        nitrogen compound source,    -   wherein there is provided a step, after said step of growing        said semiconductor layer containing Al but before a start of        said step of growing said active layer, of removing one or more        of an Al source, an Al reactant, an Al compound, and Al        remaining in said growth chamber, from a part of said growth        chamber that can make a contact with said nitrogen compound        source or an impurity contained in said nitrogen compound        source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that explains this background of the invention;

FIG. 2 is a diagram that shows the constitution of a conventional MOCVDapparatus;

FIG. 3 is a diagram that shows the constitution of a conventional MBEapparatus;

FIG. 4 is a diagram that explains the principle of this invention;

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DETAILED DESCRIPTION OF THE INVENTION

FIG. 5 shows an example of a semiconductor light-emitting device havinga semiconductor layer containing Al between a substrate and asemiconductor layer containing N.

Referring to FIG. 5, the semiconductor light-emitting device isconstructed on a substrate 201 and includes a first semiconductor layer202 containing Al formed on the substrate 201, wherein the firstsemiconductor layer 202 further carries consecutively thereon anintermediate layer 203, an active layer 204 containing N, anotherintermediate layer 203, and a second semiconductor layer 205.

The substrate 201 may be formed of a compound semiconductor materialsuch as GaAs, InP, GaP, and the like, while the first semiconductorlayer 202 may be formed of any of AlAs, AlP, AlGaAs, AlInP, AlGaInP,AlInAs, AlInAsP, AlGaInAsP, and the like. The first semiconductor layer202 may be formed of a single layer or plural layers each containing Alas a constituent element.

The intermediate layer 203, on the other hand, is free from Al and maybe formed of a material such as GaAs, GaP, InP, GaInP, GaInAs, GaInAsP,and the like.

The nitrogen-containing active layer 204 may be formed of any of GaNAs,GaPN, GaInNAs, GaInNP, GaNAsSb, GaInNAsSb, and the like, wherein theactive layer 204 is grown without introducing an Al source during thegrowth process thereof. The active layer 204 may be formed of a singlelayer or a quantum well layer containing nitrogen. Further, the activelayer 204 may have a multilayer quantum well structure in which a numberof nitrogen-containing quantum well layers are repeated with interveningbarrier layers having a composition identical with that of theintermediate layer.

In the construction of FIG. 5, it should be noted that the energybandgap increases in the order of active layer 204, the intermediatelayer 203, the first semiconductor layer 202 and the secondsemiconductor layer 205. Generally, the second semiconductor layer 205is formed of the same material forming the first semiconductor layer202, while this is not a prerequisite. Further, the layer 205 may beformed of a material free from Al.

The semiconductor light-emitting device of FIG. 5 can be formed byconducting a crystal growth process in an epitaxial growth apparatuswhile using a metal organic Al source and a nitrogen compound source.For example, it is possible to use TMA (trimethyl aluminum) or TEA(trimethyl aluminum) for the metal organic source of Al. Further, anorganic nitrogen source such as DMHy (dimethyl hydrazine) or MMHy(monomethyl hydrazine), or NH3 may be used for the nitrogen sourcecompound. The crystal growth is conducted typically by an MOCVD processor CBE (chemical beam epitaxy) process.

FIG. 6 shows the depth profile of nitrogen and O measured for thestructure of FIG. 5 for the case the semiconductor device is formed in asingle epitaxial growth (MOCVD) apparatus by using AlGaAs for the firstand second semiconductor layers 202 and 205, GaAs for the intermediatelayer 203, and a GaInNAs/GaAs double quantum well structure for theactive layer 204. The measurement of FIG. 6 was conducted by a SIMSanalysis under a condition summarized in Table 1.

TABLE 1 primary ion specie Cs⁺ primary acceleration voltage 3.0 kVsputter rate 0.5 nm/s measurement area 160 × 256 μm² vacuum <3E−7 Papolarity of measurement ions —

Referring to FIG. 6, it can be seen that there are two nitrogen peaks inthe active layer 204 in correspondence to the GaInNAs/GaAs doublequantum well structure. Further, FIG. 6 shows the existence of an oxygenpeak generally in correspondence to the active layer 204. Furthermore,it is noted that the oxygen concentration of the Al-free intermediatelayer 203 is one order smaller than the oxygen concentration of theactive layer 204.

In the case the same structure is formed while using GaInP for the firstand second semiconductor layers 202 and 205, on the other hand, itturned out that the oxygen concentration in the active layer 204 was inthe background level.

Thus, by the foregoing experiments of the inventor, it was establishedthat oxygen is incorporated into the active layer 204 in the event thesemiconductor device of FIG. 5, in which the semiconductor layer 202containing Al is interposed between the substrate 201 and the activelayer 204, is grown consecutively on the substrate 201 in a singleepitaxial growth apparatus while using a nitrogen compound source and ametal organic source.

The oxygen atoms thus incorporated into the active layer 204 formnon-optical recombination levels therein, and because of this, theefficiency of optical emission of the active layer 204 is deterioratedseverely. Thus, it was established that the oxygen atoms thusincorporated into the active layer at the time of growth of the activelayer on an Al-containing semiconductor layer are the cause of thedegradation of efficiency of optical emission in the semiconductorlight-emitting device of FIG. 5 or a semiconductor light-emitting devicehaving a similar structure.

When the layered structure of FIG. 5 is grown by an MBE process, on theother hand, there is no such a report of degradation of efficiency ofoptical emission, even in the case there has been provided anAl-containing semiconductor layer between the substrate and thenitrogen-containing active layer. Thus, the problem of degradation ofefficiency of optical emission has been the problem peculiar to thesemiconductor devices having an Al-containing semiconductor layerbetween a substrate and an active layer and formed by an MOCVD processwhile using a metal organic source of Al and a nitrogen compound source.

The present invention explained hereinafter is based on the foregoingdiscovery of the inventors of the present invention.

[First Mode of Invention]

In a first mode, the present invention provides a semiconductorlight-emitting device comprising: a substrate; an active layercontaining nitrogen; and a semiconductor layer containing Al interposedbetween the substrate and the active layer, wherein the semiconductordevice has a characteristic feature of the active layer containingoxygen with a concentration level such that there occurs a continuouslaser oscillation in the semiconductor device at room temperature.

Table 2 below shows the comparison of threshold current density of laseroscillation for the various laser diodes having an AlGaAs cladding layerin combination with an active layer of a GaInNAs double quantum wellstructure with various oxygen concentrations in the AlGaAs claddinglayer. In the experiments of Table 2, it should be noted that the laserdiode was constructed in the form of broad stripe laser diode and thethreshold current density was evaluated by causing a pulse laseroscillation at room temperature.

TABLE 2 threshold O concentration current in active layer densitythreshold cladding [cm-3] [kA/cm2] characteristic AlGaAs 1.5E+18  nooscillation X AlGaAs  9E+17 2–3 ◯ AlGaAs  3E+17 0.8 ⊚ AlGaAs <2E+17 0.8⊚ GaInP <2E+17 0.8 X poor ◯ good ⊚ excellent

From Table 2, it can be seen that, in the structure in which anitrogen-containing active layer is grown continuously on asemiconductor layer containing Al as a constituent element, thethreshold of laser oscillation is very large due to the very largeoxygen concentration level of 1.5×10¹⁸ cm⁻³ and no laser oscillation wasobserved even when a drive current of 10 kA/cm² is supplied.

When the oxygen concentration level in the active layer is reduced to alevel of 9×10¹⁷ cm⁻³, on the other hand, it was observed that thethreshold current of laser oscillation is decreased to 2–3 kA/cm² andthe pulse laser oscillation became possible. In a broad stripe laserdiode, a continuous laser oscillation at room temperature becomespossible when an active layer that has achieved the threshold currentdensity of 3 kA/cm² or less is used. Thus, by suppressing the oxygenconcentration level in the nitrogen-containing active layer to 1.5×10¹⁸cm⁻³ or less, it becomes possible to produce a laser diode capable ofperforming continuous laser oscillation at room temperature.

[Second Mode of Invention]

In a second mode, the present invention provides a semiconductorlight-emitting device similar to the one used in the first mode of theinvention wherein there is provided an intermediate layer between asemiconductor layer containing Al and an active layer containingnitrogen, and wherein the active layer has an oxygen concentration levelsubstantially identical to or smaller than the oxygen concentrationlevel of the intermediate layer.

Here, it should be noted that the intermediate layer is formed of anAl-free material, and the semiconductor layer containing Al and theactive layer containing nitrogen are separated from causing a directcontact from each other as a result of formation of the Al-freeintermediate layer. By doing so, exposure of reactive Al surface isavoided at the time of supplying a nitrogen compound source for growingthe nitrogen-containing active layer, and the segregation of nitrogenatoms at the interface between the Al-containing semiconductor layer andthe nitrogen-containing active layer as a result of strong Al-nitrogenbonding is avoided.

In the case an active layer free from nitrogen such as a GaAs or GaInAsactive layer is formed by an MOCVD process on a semiconductor layercontaining Al, there has been no report about the degradation of theefficiency of optical emission. Thus, by reducing the oxygen content inthe nitrogen-containing active layer to the level of the intermediatelayer free from nitrogen, it becomes possible to obtain a high-qualityactive layer free from oxygen degradation.

From the depth profile of oxygen of FIG. 6, it can be seen that theintermediate layer 203 contains oxygen with the level of 2×10¹⁷–7×10¹⁶cm⁻³. Thus, by reducing the oxygen concentration level of the activelayer 204 to the level of 2×10¹⁷ cm⁻³ or less, a high quality activelayer suitable for efficient laser oscillation is obtained.

FIG. 7 shows the photoluminescent spectrum of the GaInNAs/GaAs doublequantum well structure.

Referring to FIG. 7, the continuous line represents the case in whichthe GaInNAs/GaAs double quantum well active layer 204 is formed on thefirst semiconductor layer 202 of AlGaAs with the GaAs intermediate layer203 interposed between the semiconductor layer 202 and the active layer204, while the dotted line represents the case in which a GaInP layer isused for the semiconductor layer 202 and the GaInNAs/GaAs double quantumwell active layer 204 is formed directly on the GaInP layer 202.

Referring to FIG. 7, it can be seen that a photoluminescence intensitysubstantially identical with the photoluminescence intensity for thecase a GaInNAs/GaAs double quantum well active layer 204 is formed on aGaInP layer 202 is achieved also in the case of growing the samenitrogen-containing active layer 204 on an Al-containing semiconductorlayer 202, by reducing the oxygen concentration level in theGaInNAs/GaAs active layer 204 to the level of 2×10¹⁷ cm⁻³ or less.

As represented in Table 2, the threshold current density of laseroscillation is reduced further to the level of 0.8 kA/cm² by reducingthe oxygen concentration level in the active layer to the level 3×10¹⁷cm⁻³ or less, wherein it should be noted that the foregoing level of 0.8kA/cm² is the threshold current level achieved when a GaInP claddinglayer is used.

Thus, by suppressing the oxygen concentration level in thenitrogen-containing active layer to the level of 3×10¹⁷ cm⁻³ or less, aphotoemission characteristic equivalent to the photoemissioncharacteristic for the case the semiconductor light-emitting device isconstructed on an Al-free semiconductor layer is achieved.

[Third Mode of Invention]

FIG. 8 shows the depth profile of Al obtained for the semiconductorlight-emitting device of FIG. 5 for the case AlGaAs is used for thefirst semiconductor layer 202 and the second semiconductor layer 205,GaAs is used for the intermediate layer 203 and a GaInNAs/GaAs doublequantum well structure is used for the active layer 204, wherein thelayered structure of FIG. 5 is formed in a single epitaxial growth(MOCVD) apparatus and the measurement was conducted by a SIMS analysisunder the measurement condition summarized in Table 3 below.

TABLE 3 primary ion specie O₂ ⁺ primary acceleration voltage 5.5 kVsputter rate 0.3 nm/s measurement area 60 μmΦ vacuum <3E−7 Pa polarityof measurement ions +

From FIG. 8, it can be seen that Al is detected in the active layer 204,which is supposed as being inherently free from Al, as no Al source isused in the growth process of the active layer 204. On the other hand,the Al concentration level in the intermediate layer 203 adjacent to theAl-containing semiconductor layer 202 or 205 is lower than the activelayer 204 by a factor of ten. The foregoing result clearly indicatesthat Al in the active layer 204 does not have the origin in theAl-containing semiconductor layer 202 or 205.

In the case a nitrogen-containing active layer 204 is grown on asemiconductor layer free from Al such as a GaInP layer, on the otherhand, no Al was detected in the active layer 204.

Thus, it is concluded that Al detected in the active layer in the SIMSprofile of FIG. 8 is originated from residual Al species remaining inthe growth chamber after the growth of the Al-containing layer iscompleted, such as a residual Al source material, a residual Alreactant, a residual Al compound, or residual Al, and has beenincorporated into the active layer in the form coupled with the nitrogencompound source or an impurity such as water contained in the nitrogencompound source. Thus, when there remains such Al species in the growthchamber, these Al species are inevitably incorporated into thenitrogen-containing active layer as a result of continuous growthprocess of the nitrogen-containing active layer conducted on theAl-containing semiconductor layer, as long as the growth process isconducted in a single epitaxial growth apparatus.

Comparing the depth profile of Al of FIG. 8 with the depth profile of Oand nitrogen of FIG. 6 for the same specimen, it can be seen that theoxygen peak in the double quantum well active layer 204 does not exactlycorrespond with the nitrogen peak profile but does coincide with the Alconcentration profile of FIG. 8.

Thus, it is clear that, in the GaInNAs quantum well layer of the activelayer 204, the oxygen impurity is coupled not with nitrogen but with Althat is incorporated into the active layer 204. Thus, when residual Alspecies such as the residual source, residual Al reactant, residual Alcompound or residual Al remaining in the growth chamber has made acontact with the nitrogen compound source, water contained in thenitrogen compound source or water or oxygen remaining in the gas line orreaction tube makes a coupling with such a residual Al species, andthus, Al and oxygen are incorporated into the active layer 204simultaneously. Oxygen thus incorporated into the active layer 204 hasbeen the cause of the severe degradation of optical emission efficiencynoted before.

Table 4 below shows the threshold current density of laser oscillationfor a broad stripe laser diode in which a GaInNAs/GaAs double quantumwell structure is used for the active layer and AlGaAs is used for thecladding layer.

TABLE 4 threshold Al concentration O concentration current in activelayer in active layer density cladding [cm⁻³] [cm⁻³] [kA/cm²] AlGaAs 2.E+19 1.5E+18 >10 AlGaAs  9E+18  9E+17 2–3 AlGaAs <1.5E+18   <2E+170.8 GaInP <2E+17 <2E+17 0.8

Referring to Table 4, it was confirmed that the threshold current oflaser oscillation exceeds 10 kA/cm² in the structure in which the activelayer containing nitrogen is grown continuously on the Al-containingsemiconductor layer. In the case the Al concentration in the activelayer is reduced to the level of 2×10¹⁸ cm⁻³, on the other hand, theoxygen concentration level in the active layer is reduced to the levelof 1.5×10¹⁸ cm⁻³, and laser oscillation was achieved in the broad stripelaser diode. As noted before, a continuous laser oscillation at roomtemperature becomes possible when the threshold current density of thestripe laser diode is 3 kA/cm² or less. Thus, by suppressing the Alconcentration level of the nitrogen-containing active layer below thelevel of 2×10¹⁹ cm⁻³, it becomes possible to achieve a continuous laseroscillation at room temperature.

Thus, in the third mode of the present invention, it becomes possible toconstruct a semiconductor light-emitting device that achieves continuouslaser oscillation at room temperature by controlling the Alconcentration level of the nitrogen-containing active layer to the levelbelow 2×10¹⁹ cm⁻³.

[Fourth Mode of Invention]

In a fourth mode, the present invention provides a semiconductorlight-emitting device comprising a semiconductor layer 202 containingAl, an active layer 204 containing nitrogen and an intermediate layer203 provided between said semiconductor layer and said active layer,wherein the active layer 204 has an Al concentration level equal to orsmaller than an Al concentration level of the intermediate layer 203.

The intermediate 203 is formed of a material free from Al and separatesthe Al-containing semiconductor layer 202 and the nitrogen-containingactive layer 204 such that the Al-containing semiconductor layer 202 isprevented from making a contact with the nitrogen-containing activelayer 204. By doing so, exposure of Al, which has a strong affinity withnitrogen, is avoided when supplying a nitrogen source to the growthchamber for growth of the nitrogen-containing active layer 204, and theproblem of segregation of nitrogen at the interface between the activelayer 204 and the underlying Al-containing semiconductor layer 202 iseffectively eliminated.

From FIG. 8, it can be seen that the intermediate layer 203 grownwithout supplying any of the nitrogen compound source and the metalorganic source of Al is in the level of 1.5×10¹⁸ cm⁻³ or less. Bysuppressing the Al concentration level incorporated into the activelayer 204 to the level of 1.5×10¹⁸ cm⁻³ or less, it is possible tosuppress the oxygen concentration in the active layer 2041 to the levelof 2×10¹⁷ cm⁻³.

Further, as represented in Table 4, a threshold current density of 0.8kA/cm² is achieved of the broad stripe laser diode when the Alconcentration level in the active layer 204 is reduced to the level of1.5×10¹⁸ cm−3 or less, wherein it should be noted that this thresholdcurrent density is equivalent to the threshold current density achievedwhen a GaInP cladding layer is used for the layer 202 or 205.

Thus, by setting the concentration of Al in the nitrogen-containingactive layer 204 to the level of 1.5×10¹⁸ cm⁻³ or less, and thus equalto or smaller than the concentration of Al in the intermediate layer203, it is possible to achieve a optical emission efficiency equivalentto the case in which the active layer is formed on a semiconductor layerfree from Al.

[Fifth Mode of Invention]

In a fifth mode, the present invention provides a method of fabricatinga semiconductor device in any of the first through fourth mode of theinvention wherein the crystal growth process from the step of growingthe Al-containing semiconductor layer 202 up to the step of growing thenitrogen-containing active layer is conducted in a growth chamberwithout taking out the substrate into the atmosphere.

In the literature noted above (Electronic. Lett., 2000, 36(21),pp.1776–1777), it is noted that the growth of the Al-containingsemiconductor layer and the growth of the nitrogen-containing activelayer are achieved in respective, different MOCVD apparatuses forimproving the efficiency of optical emission of the active layer.

Contrary to this, the fifth mode of the present invention uses a singlecrystal growth apparatus and still achieves the decrease of the Alconcentration in the nitrogen-containing active layer to the level of1×10¹⁹ cm⁻³ or less in spite of the fact that a continuous crystalgrowth process is conducted after the growth of the Al-containingsemiconductor layer 202. With the decrease of the Al concentration levelto the foregoing level of 1×10¹⁹ cm⁻³ or less, the oxygen concentrationlevel in the nitrogen-containing active layer 204 is reduced to thelevel of 1×10¹⁸ cm⁻³ or less, and it becomes possible to perform thecontinuous laser oscillation at room temperature. According to thepresent mode of the invention, it is possible to simplify thefabrication process of the semiconductor light-emitting device and theproduction cost thereof is reduced.

[Sixth Mode of Invention]

As noted before, it was discovered by the inventors of the presentinvention that there remains Al species such as Al source, Al reactant,Al compound or Al in the growth chamber when a semiconductor layercontaining Al is grown. Thus, when a nitrogen compound source issupplied to the reaction chamber thereafter for growing an active layercontaining nitrogen, there occurs coupling between the nitrogen sourcecompound or impurity contained in the nitrogen source compound and theAl species, and the Al species are incorporated into the active layertogether with the nitrogen source compound.

Thereby, the Al species cause a reaction with water contained in thenitrogen source compound or oxygen remaining in the gas line or reactiontube, and thus, oxygen is also incorporated into the active layer asimpurity. Thereby, the efficiency of optical emission of the activelayer is deteriorated severely.

Thus, in the sixth mode, the present invention provides a fabricationprocess of a semiconductor light-emitting device in which there isprovided a step of removing residual Al species, such as residual Alsource, residual Al reactant, residual Al compound or residual Al, fromthe location of the growth chamber in which there is a possibility ofmaking a contact with the nitrogen compound source or impurity containedin the nitrogen compound source. As a result, the reaction between thenitrogen compound source or the impurity contained in the nitrogensource compound with the residual Al species is suppressed, and theconcentration of Al and oxygen incorporated into the active layer isreduced successfully.

By suppressing the Al concentration in the nitrogen-containing activelayer to the level of 2×10¹⁹ cm⁻³ or less, it becomes possible toachieve a continuous room temperature laser oscillation. Further, byreducing the Al concentration in the nitrogen-containing active layer tothe level of 1.5×10¹⁸ cm⁻³ or less, optical emission efficiencyequivalent to the case in which the active layer is formed on an Al-freesemiconductor layer, has been achieved.

[Seventh Mode of Invention]

In a seventh mode, the present invention provides a more practicalmodification of the sixth mode of the invention in that there isprovided a purging process of the residual Al species remaining in thegrowth chamber after the growth of the Al-containing semiconductor layerfrom the location which may make a contact with the nitrogen compoundsource or the impurity contained in the nitrogen compound source, byusing a carrier gas.

It should be noted that the purging process starts in response to thecompletion of growth of the Al-containing semiconductor layer and hencein response to the interruption of supply of the Al source material tothe growth chamber and continues up to the moment in which the supply ofthe nitrogen compound source to the growth chamber is started for thegrowth of the nitrogen-containing active layer.

With the growth of the Al-containing layer, residual Al species remainin the growth chamber as noted already, while the present inventionsuccessfully reduce the concentration of the residual Al species in thegrowth chamber by purging the growth chamber with the carrier gas.

Table 5 below shows the relationship between the purging duration andthe Al concentration level in the active layer for the semiconductorlight-emitting device produced by the inventors of the present inventionin an MOCVD apparatus. Similarly as before, the semiconductorlight-emitting device includes a nitrogen-containing active layercorresponding to the layer 204 of FIG. 5 formed on an Al-containingsemiconductor layer 202, wherein the Al purging process is conductedbetween the growth of the Al-containing semiconductor layer 202 and thenitrogen-containing active layer 204.

TABLE 5 purge time Al concentration in active layer (minute) [/cm³]5 >5E+19  10 8.E+18 30 1.E+18 60 3.E+17

From Table 5, it can be seen that the Al concentration in the activelayer is reduced to the level of 1×10¹⁹ cm⁻³ or less by conducting thepurging process of about 10 minutes. Thus, by using the purging processof 10 minutes or more, it becomes possible to provide a semiconductorlight-emitting device capable of oscillating continuously at roomtemperature.

The result of Table 5 also indicates that it is possible to reduce theAl concentration in the active layer to the level of 1×10 ¹⁸ cm⁻³ orless by conducting the purging process for 30 minutes or more. Withthis, it becomes possible to achieve an efficiency of optical emissionequivalent with the case in which the nitrogen-containing active layeris formed on an Al-free semiconductor layer.

FIG. 9 shows the construction of a semiconductor light-emitting deviceaccording to the seventh mode of the invention, wherein those partscorresponding to the parts described previously are designated by thesame reference numerals.

Referring to FIG. 9, the semiconductor light-emitting device isconstructed on the substrate 201 that carries thereon the firstsemiconductor layer 202, wherein the first semiconductor layer 202contains Al as a constituent element. On the semiconductor layer 202,there are formed first and second lower intermediate layers 601 and 602consecutively, and the active layer 204 is formed on the second layerintermediate layer 602. Further, the upper intermediate layer 203 andthe second semiconductor layer 205 are formed on the active layer 204.

The structure of FIG. 8 is formed by conducting an epitaxial growthprocess while using a metal organic Al source and an organic nitrogensource, wherein there is provided a growth interruption process afterthe growth of the first lower intermediate layer 601 but before thegrowth of the second intermediate layer 602. During the growthinterruption process, the residual Al species such as residual Alsource, residual Al reactant, residual Al compound or residual Al, areremoved at least from the location of the growth chamber which may makea contact with the nitrogen compound source and hence the impuritycontained in the nitrogen compound source, by conducting a purgingprocess that uses a hydrogen gas as a purging gas.

FIG. 10A shows the depth profile of Al for the specimen of FIG. 9 forthe case the purging process is conducted for 60 minutes between thefirst and second lower intermediate layers 601 and 601.

Referring to FIG. 10A, it can be seen that the Al concentration in theactive layer 204 is reduced to the level of 3×10¹⁷ cm⁻³ or less byconducting the purging process for 30 minutes. This Al concentrationlevel is equivalent to the Al concentration level in the intermediatelayers 601 and 602.

FIG. 10B shows the depth profile of nitrogen and O in the same device ofFIG. 9.

Referring to FIG. 10B, it can be seen that the oxygen concentration inthe active layer 204 is reduced to the background level of 1×10¹⁷ cm⁻³.

It should be noted that the oxygen peak appearing in the lowerintermediate layers 601 and 602 reflects the oxygen segregation causedin the growth interruption surface.

Thus, in the present mode of invention, it is possible to reduce theimpurity concentration level of Al or oxygen in the nitrogen-containingactive layer 204 by providing an interruption of growth in the firstlower intermediate layer 601 and the second intermediate layer 602 andconducting a purging process for 60 minutes. With this, it becomespossible to improve the efficiency of optical emission of thenitrogen-containing active layer 204.

In the purging process of the growth chamber, it is possible to carryout the purging process while heating the susceptor, which is used forheating the substrate in the growth chamber. The susceptor may be heatedby any of high-frequency induction heating process or resistance heatingprocess. Alternatively, the susceptor may be heated by using a lamp. Thesubstrate may be heated in direct contact with the susceptor or via atransportation tray disposed between the substrate and the susceptor.

By purging the interior of the growth chamber by the carrier gas in thestate that the susceptor is heated, the Al species adsorbed on thesusceptor or the part located in the vicinity of the susceptor aredegassed, and the removal of the Al species is conducted efficiently.With this, the duration for removal of the purging process can bereduced.

In the foregoing process in which the substrate is heatedsimultaneously, it is necessary to continue supplying the group V sourcesuch as AsH₃ or PH₃ to the growth chamber also in the interval of thegrowth interruption for avoiding thermal decomposition of thesemiconductor layer 205.

During the purging process of the growth chamber, it is also possible totransport the substrate from the growth chamber to another chamber. Bydoing so, it is no longer necessary to continue supplying the group Vsource gas such as AsH₃ or PH₃ during the purging process even when thesusceptor is heated during the purging process. Thereby, thermaldecomposition of the Al species deposited on the susceptor or the partnear the susceptor is facilitated and the concentration of the Alspecies in the growth chamber is reduced efficiently.

In the case a transportation tray is used, it is preferable to heat thetransportation tray together with the susceptor. With this, it becomespossible to remove the Al species adsorbed on the transportation trayeffectively.

Thus, by conducting the purging process of the residual Al species fromthe location of the growth chamber that may make a contact with thenitrogen compound source and hence the impurity contained in thenitrogen compound source, after the growth of the Al-containingsemiconductor layer such as an AlGaAs cladding layer but before thestart of growth of the nitrogen-containing active layer such as aGaInNAs active layer, in the state that the susceptor is heated, itbecame possible to achieve a threshold current of laser oscillationequivalent to a laser diode having a GaInP cladding layer in a broadstripe laser diode.

[Eighth Mode of Invention]

In an eighth mode, the present invention provides a fabrication processaccording to the seventh mode including the purging process for purgingthe residual Al species from the location of the growth chamber that maycontact with the nitrogen compound source of the impurity contained inthe nitrogen compound source by using a carrier gas, wherein the purgingprocess is conducted while conducting the growth of the intermediatelayer.

Thus, in the semiconductor light-emitting device of FIG. 9, the purgingprocess was conducted in the growth interruption period provided afterthe growth of the first lower intermediate layer 601 but before thegrowth of the second lower intermediate layer 602, as explained before.

In the eighth mode of the invention, on the other hand, there is no needof providing such a growth interruption, and the Al-purging process isconducted while growing the intermediate layer simultaneously. It shouldbe noted that the intermediate layer is free from Al, and thus, there isno risk of introducing an Al source material into the growth chamberduring the growth process of the intermediate layer. Thus, it becomespossible to carry out the purging process of the Al species whileconducting the growth of the intermediate layer.

In the case the interruption of growth is continued over a long timeperiod in the sixth mode of the invention, there is a risk that thegrowth interruption surface may experience segregation of impuritiessuch as O, C, Si, and the like. With this, there is a possibility offormation of non-optical recombination centers on such a growthinterruption surface. The present mode of the invention can successfullyovercome this problem by continuing the growth of the intermediate layerwhile simultaneously conducting the purging process.

In the case of conducting the purging of the growth chamber whilecontinuing the growth of the intermediate layer to the thickness of 0.1μm, a purge duration exceeding 10 minutes can be secured by lowering thegrowth rate of the intermediate layer to 0.6 μm/h or less. By reducingthe growth rate of the intermediate layer to 0.2 μm/h or less, itbecomes possible to conduct the purging process for a duration exceeding30 minutes. With this, the Al concentration in the active layer isreduced to the level of 1×10¹⁸ cm⁻³ or less.

In the case the growth rate of 2 μm/h, which is a typical growth rate ofan MOCVD process, is to be maintained, a sufficient purge duration issecured by forming the lower intermediate layer to have a thickness of0.33 μm or more, preferably 1.0 μm or more.

Thus, by suitably choosing the thickness of the lower intermediate layerand the growth rate thereof, it becomes possible in the present mode ofthe invention to secure a purge duration of 10 minutes or more, and itbecomes possible to reduce the Al concentration level in the activelayer to 1×10¹⁹ cm⁻³ or less. Thereby, it becomes possible to achieve acontinuous laser oscillation at room temperature. By using the purgeduration of 30 minutes or more, it becomes possible to achieve a lasercharacteristic equivalent with that of a laser diode formed on anAl-free semiconductor layer.

In the present mode of the invention, it is also possible to combine thegrowth interruption process and the purging process achieved during thegrowth of the intermediate layer. Further, it is possible to carry outthe growth interruption process and the purging process by way of thegrowth process of the intermediate layer alternately for plural times.

[Ninth Mode of Invention]

FIG. 11 show the construction of a surface-emission type semiconductorlight-emitting device according to a ninth mode of the invention,wherein those parts corresponding to the parts described previously aredesignated by the same reference numerals and the description thereofwill be omitted.

Referring to FIG. 11, the semiconductor device is constructed on thesubstrate 201 of a single crystal material and includes a lowersemiconductor multilayer reflector 801 formed on the substrate 201 and alower spacer layer 802 formed on the lower semiconductor multilayerreflector 801. The lower spacer layer 802 carries thereon theintermediate layer 203, and the nitrogen-containing active layer 204 isformed on the intermediate layer 203.

The active layer 204 is covered with the upper intermediate layer 203and an upper spacer layer 803 is formed on the upper intermediate layer203. Furthermore, an upper multilayer reflector 804 is formed on theupper spacer layer 803.

In the semiconductor device of FIG. 11, the optical beam is emitted inthe direction perpendicular to the substrate 201.

In the structure of FIG. 11, GaAs is used for the single crystalsubstrate 201, and the lower multilayer reflector 801 is formed ofalternate stacking of a semiconductor layer of high refractive index anda semiconductor layer of low refractive index, each having an opticalthickness of one-quarter of the oscillation wavelength of the laserdiode. Thus, the lower multilayer reflector 801 forms a distributedBragg reflector. The reflector 801 may have the combination of highrefractive index layer and low refractive index layer (high refractiveindex layer/low refractive index layer) such as: GaAs/AlxGa1-xAs(0≦x≦1); AlxGa1-xAs/AlyGa1-yAs (0<x<y≦1); and GaInP/(AlxGa1-x)InP(0<x≦1).

In the structure of FIG. 11, the region between the reflectors 801 and804, including the lower spacer layer 802 and the upper spacer layer803, form an optical cavity, wherein the optical cavity is formed tohave an optical thickness of an integer multiple of one-half of thelaser oscillation wavelength. The intermediate layer 203 is formed of amaterial free from Al such as GaAs, GaInP or GaInAsP.

The nitrogen-containing active layer 204 may be formed of any of GaNAs,GaInNAs, GaNAsSb, GaInNAsSb, and the like. It should be noted that suchnitrogen-containing III–V mixed crystal has a bandgap wavelength of1.2–1.6 μm and can be grown epitaxially on a GaAs substrate. The activelayer 204 is not limited to a single bulk layer but may be constructedin the form of single or multiple quantum well structure that includes aquantum well layer of a semiconductor material containing nitrogen.

The upper multilayer reflector 804B is formed also of a distributedBragg reflector similarly to the case of the lower multilayer reflector801. In the case of the upper multilayer reflector 804, it is alsopossible to construct the distributed Bragg reflector by semiconductorlayers as in the case of the lower multilayer reflector 804 or in theform of stacking of dielectric materials such as SiO₂/TiO₂.

By using a semiconductor layer containing Al for the low refractiveindex layer of the lower semiconductor multilayer reflector 801, thedifference of refractive indeed between the high refractive index layerand the low refractive index layer is maximized and a reflectance of 99%or more is achieved with reduced number of the layers. With decrease inthe number of the layers in the reflector, the electrical resistance andthermal resistance caused by the reflector are reduced and thetemperature characteristics of the laser diode are improved.

In the case of an edge-emission laser diode, it is possible form thecladding layer by an Al-free material such as GaInP, InP, GaInAsP, andthe like. In the case of a surface emission laser diode, on the otherhand, it is inevitable to use an Al-containing semiconductor layer forthe low refractive index layer of the lower semiconductor multilayerreflector in order to guarantee the operational temperature range of 70°C. or more.

Thus, the degradation of efficiency of optical emission of thenitrogen-containing active layer becomes a particularly serious problemin the surface-emission laser diode that uses an nitrogen-containingactive layer on the lower semiconductor multilayer reflector 801containing Al. In the present invention, a continuous laser oscillationat room temperature becomes possible, by reducing the Al concentrationin the nitrogen-containing active layer 204 to the level of 1×10¹⁹ cm⁻³or less. With this, the O concentration in the active layer 204 isreduced to the level of 1×10¹⁸ cm⁻³ or less, and the laser diode canoscillate continuously at room temperature. By reducing the Alconcentration in the active layer 204 further to the level of 2×10¹⁸cm⁻³ or less, and thus by reducing the O concentration in the activelayer 204 to the level of 2×10¹⁷ cm⁻³ or less, an optical emissioncharacteristic equivalent to the device in which the active layer isformed on an Al-free semiconductor layer is achieved. With this, itbecomes possible to realize a surface-emission laser diode thatoscillates continuously up to the temperature of 70° C. or more.

In the case of constructing the nitrogen-containing active layer 204 byany of GaNAs, GaInNAs, GaNAsSb, GaInNAsSb, and the like, it is possibleto construct a long-wavelength surface-emission laser diode operable atthe wavelength band of 1.2–1.6 μm on a GaAs substrate. As thesurface-emission laser diode of the present invention can use thematerial system of GaAs/AlGaAs, which is characterized by highreflectance and low resistance, for the lower semiconductor multilayerreflector 801, it is possible to realize a long-wavelengthsurface-emission laser diode having excellent temperaturecharacteristics.

It should be noted that the wavelength band of 1.2–1.6 μm is the bandsuitable for optical transmission via a single-mode optical fiber. Thus,the surface-emission laser diode of the present invention can be used asan optical source of a large-capacity optical LANs of medium to shortdistance range.

In the foregoing modes of the invention, it has been assumed that oxygenis the impurity element that forms the non-recombination centers in thenitrogen-containing active layer and the description was made such thatthe oxygen concentration level in the nitrogen-containing active layeris suppressed below a predetermined level necessary for achieving roomtemperature continuous laser oscillation of the semiconductorlight-emitting device. The present invention, however, is not limited tothis particular case and is applicable also to the case in which theelement forming the non-optical recombination centers is not oxygen. Inthis case, too, the efficiency of optical emission is improved byreducing the concentration of the impurity element in thenitrogen-containing active layer to a predetermined level, and acontinuous room temperature laser oscillation is achieved successfully.

Further, in the present invention, it is possible to achieve an opticalemission efficiency equivalent to the optical emission efficiency in thecase the active layer is formed on an Al-free semiconductor layer alsoin the case the impurity element that causes the non-opticalrecombination of carriers in the active layer is not oxygen, by reducingthe concentration level of the impurity element in thenitrogen-containing active layer to the level of the intermediate layeror less.

<Embodiment 1>

FIG. 12 shows the construction of a laser diode according to Embodiment1 of the present invention.

Referring to FIG. 12, the laser diode is constructed on a GaAs substrate901 of n-type and includes a buffer layer 902 of n-type GaAs formed onthe substrate 901, a cladding layer 903 of n-type AlGaAs having acomposition of Al_(0.4)Ga_(0.6)As formed on the buffer layer 902, afirst lower optical waveguide layer 904 of GaAs formed on the AlGaAscladding layer 903 and a second lower optical waveguide layer 905 ofGaAs formed on the optical waveguide layer 904, and an active layer 906of GaInNAs/GaAs multiple quantum well structure is formed on the secondlower optical waveguide layer 905.

On the active layer 906, an upper optical waveguide layer 907 of GaAs isformed and a cladding layer 908 of p-type AlGaAs having the compositionof Al_(0.4)Ga_(0.6)As is formed on the upper optical waveguide layer907. Further, a contact layer 909 of p-type GaAs is formed on thecladding layer 908.

The layered structure thus formed is subjected to a mesa etching processfrom the surface of the contact layer 909 up to an intermediate level ofthe cladding layer 908 to form a ridge stripe structure with a stripewidth of 4 μm.

On the contact layer 909, there is formed a p-side electrode 910, and ann-side electrode 911 is formed on a bottom surface of the GaAs substrate901.

Thus, the laser diode of FIG. 12 is a ridge stripe laser diode in whichthe electric current and optical radiation are confined in the ridgestripe structure.

In Embodiment 1, the growth of the layered structure of FIG. 12 isconducted by using a single MOCVD apparatus while using TMG, TMA and TMIfor the group III source and AsH₃ and DMHy as the group V source. In thegrowth process of the structure of FIG. 12, it should be noted thatinterruption of growth is made after the growth of the first loweroptical waveguide layer 904 but before the start of growth of the secondlower optical waveguide layer 905.

During the foregoing interruption period of growth, the growth chamberis purged by the carrier gas in the state that the substrate is held inthe growth chamber. With this purging process, any residual Al-speciesremaining in the growth chamber, such as residual Al source, residual Alreactant, residual Al compound or residual Al, are removed and the Alconcentration level in the growth chamber is reduced.

By growing the GaInNAs/GaAs multiple quantum well active layer 906 aftersuch an interruption of growth, the problem of Al and oxygenincorporation into the GaInNAs quantum well layer is successfullysuppressed. By conducting such a purging process for a duration of 60minutes, the Al concentration level in the GaInNAs active layer isreduced to the level of 3×10¹⁷ cm⁻³ or less, and the oxygenconcentration is reduced to the level of 2×10¹⁷ cm⁻³ or less.

With this, the efficiency of optical emission of the nitrogen-containingactive layer 906 is improved and the ridge stripe laser diode oscillatescontinuously at room temperature.

<Embodiment 2>

FIG. 13 shows the construction of a surface-emission laser diodeaccording to Embodiment 2 of the present invention, wherein those partscorresponding to the parts described previously are designated by thesame reference numerals and the description thereof will be omitted.

Referring to FIG. 13, the surface-emission laser diode is constructed onthe GaAs substrate 901 of n-type and includes a semiconductor multilayerreflector 1001 of n-type formed on the substrate 901, wherein a firstlower spacer layer 1002 of GaAs is formed on the reflector 1001 and asecond lower spacer layer 1003 of GaAs is formed further on the firstlower spacer layer 1002. The nitrogen-containing active layer 906 ofGaInNAs/GaAs multiple quantum well structure is formed on the secondlower spacer layer 1003, and an upper spacer layer 1004 of GaAs isformed on the active layer 906. Further, an AlAs selective oxidationlayer 1005 is formed on the upper spacer layer 1004 and a p-typesemiconductor multilayer reflector 1006 is formed on the AlAs selectiveoxidation layer 1005.

The n-type semiconductor multilayer reflector 1001 is formed of adistributed Bragg reflector in which a GaAs high refractive index layerof n-type and an Al_(0.8)Ga_(0.2)As low refractive index layer of n-typeare repeated alternately. Similarly, the p-type semiconductor multilayerreflector 1006 is formed of a distributed Bragg reflector in which aGaAs layer of p-type and an Al_(0.8)Ga_(0.2)As layer of p-type arerepeated alternately.

In the present embodiment, the GaInNAs/GaAs multiple quantum well activelayer 906 has a bandgap wavelength of the 1.3 μm band, and the layersfrom the first lower spacer layer 1002 up to the upper spacer layer 1004constitute a λ optical cavity.

In the laser diode of FIG. 13, the foregoing layered structure issubjected to a mesa etching process to form a cylindrical mesa having adiameter of 30 μm, such that the mesa etching reaches the n-typesemiconductor multilayer reflector 1001.

The cylindrical mesa thus formed is subjected to a lateral oxidationprocess such that there occurs a selective lateral oxidation in the AlAslayer 1005 starting from the exposed sidewall of the mesa structure. Asa result, there is formed an insulation region 1007 of AlOx in the AlAsselective oxidation layer 1005 such that the AlOx region 1007 surroundsthe AlAs core 1005. By providing such a structure, the electric currentinjected into the active layer 906 is confined to a limited regionhaving a diameter of about 5 μm corresponding to the AlAs core 1005, andthus, the AlAs core 1005 and the AlOx insulation region 1007 formtogether a current confinement structure.

In FIG. 13, it should be noted that the p-type semiconductor multilayerreflector 1006 carries a ring-shaped p-side electrode, while the GaAssubstrate 901 carries the n-side electrode 911 on the bottom surfacethereof.

In the laser diode of FIG. 13, the optical radiation produced in theGaInNAs/GaAs multiple quantum well active layer 906 is amplified as itis reflected back and forth between the semiconductor multilayerreflectors 1001 and 1006, and a laser beam having a wavelength of the1.3 μm band is emitted in the direction perpendicular to the substrate901.

In Embodiment 2, the growth of the layered structure of FIG. 13 isconducted in a single MOCVD apparatus while using TMG, TMA and TMI forthe group III source and AsH₃ and DMHy for the group V source. Duringthe growth process of the layered structure of FIG. 13, the presentinvention provides an interruption of crystal growth after the growth ofthe first GaAs lower spacer layer 1002 but before the start of growth ofthe second GaAs lower spacer layer 1003.

During the foregoing interruption period of growth, the growth chamberis purged by the carrier gas in the state that the substrate is held inthe growth chamber, and while supplying the AsH₃ gas and heating thesusceptor, for a duration of 30 minutes or more. With this purgingprocess, any residual Al-species remaining in the growth chamber, suchas residual Al source, residual Al reactant, residual Al compound orresidual Al, are removed and the Al concentration level in the growthchamber is reduced.

With this, the residual Al concentration level in the growth chamber isreduced, and it becomes possible to suppress the incorporation of Al andoxygen into the GaInNAs quantum well layer. According to a SIMS analysisconducted on the device thus formed, it was confirmed that the Alconcentration in the GaInNAs well layer is reduced to the level of2×10¹⁸ cm⁻³ or less and the oxygen concentration is reduced to the levelof 2×10 ¹⁷ cm⁻³ or less. Thus, the efficiency of optical emission in theactive layer is improved and a continuous room temperature oscillationis confirmed at room temperature at the wavelength of the 1.3 μm band.

<Embodiment 3>

FIG. 14 shows the construction of a surface-emission laser diodeaccording to Embodiment 3 of the present invention, wherein those partscorresponding to the parts described previously are designated by thesame reference numerals and the description thereof will be omitted.

Referring to FIG. 14, the laser diode of Embodiment 3 has a constructionsimilar to that of the laser diode of Embodiment 2 except that theentire layers from the lower spacer layer 1101 to the upper spacer layer1104 form an Nλ optical cavity (N=2, 3, 4, . . . ). Thus, the lowerspacer layer 1101 has a thickness d_(b) determined asd _(b)=(N−0.5)λ/n _(s)−(n _(a) /n _(s)) (d _(a)/2),wherein λ represents the laser oscillation wavelength, n_(s) representsthe refractive index of the GaAs spacer layer, n_(a) represents therefractive index of the active layer, and d_(a) represents the thicknessof the active layer. Further, the upper spacer layer 1004 has athickness d_(u) determined asd _(u)=0.5λ/n _(s)−(n _(a) /n _(s))(d _(a)/2).

In the case of N=4, λ=1300 nm, d_(a)=30 nm, the thickness of the GaAslower spacer layer 1101 is determined to be about 1.3 μm. In the casethis GaAs lower spacer layer 1101 of 1.3 μm thickness is grown with agrowth rate of 1 μm/h, it takes about 78 minutes to complete the growthof the layer 1101. In Embodiment 3, the residual Al species are purgedfrom the growth chamber during the growth process of the GaAs lowerspacer layer 1101. Thus, it is possible to conduct a purging processwith a duration exceeding 60 minutes without providing a specific growthinterruption process over a long time period.

Thus, Embodiment 3 can also reduce the Al concentration level and oxygenconcentration level incorporated in the GaInNAs quantum well layerformed on the Al-containing lower reflector 1101 and the efficiency ofoptical emission is improved.

In Embodiment 3, it should be noted that there arises no problems ofimpurity segregation in the spacer layer in view of not providing theinterruption of growth process over a long time period.

By increasing the length of the optical cavity as in the case of the Nλcavity of the present embedment, it becomes possible to maintain asingle mode operation up to high optical output even in such a case thediameter of the AlAs core layer 1005 is increased to 10 μm. Thus, itbecomes possible to provide a high-power single-mode surface-emissionlaser diode operable in the long wavelength band.

<Embodiment 4>

FIG. 15 shows the construction of a laser diode according to Embodiment4 of the present invention.

Referring to FIG. 15, the laser diode is constructed on a hexagonalsingle crystal substrate 1201 and includes a low temperature bufferlayer 1202 of AlGaN formed on the substrate 1201, wherein an n-typebuffer layer 1202 of low-temperature AlGaN and an n-type buffer layer1203 of GaN are formed consecutively on the substrate 1201. On then-type buffer layer 1203, there is provided a cladding layer 1204 ofn-type AlGaAs having a composition of Al_(0.15)Ga_(0.85)N, and an activelayer 1206 of InGaN/GaN multiple quantum well structure is formed on thecladding layer 1204 with an intervening lower optical waveguide layer1205 of GaN between the cladding layer 1204 and the active layer 1206.

On the active layer 1206, there is provided a p-type cladding layer 1208of AlGaN having the composition of Al_(0.15)Ga_(0.85)N, with anintervening GaN optical waveguide layer 1207 interposed between theactive layer 1206 and the cladding layer 1208, and a GaN contact layer1209 of p-type is provided further on the cladding layer 1208.

Any of sapphire, SiC, ZnO, GaN and AlN may be used for the hexagonalsingle crystal substrate 1201.

The layered structure thus formed is subjected to a mesa etching processfrom the p-type contact layer 1209 to an intermediate level of thecladding layer 1208, and there is formed a ridge stripe. In the presentexample, the ridge stripe is formed with a width of 3 μm.

On the p-type GaN contact layer 1209, there is formed a p-side electrode1210. Further, the structure of FIG. 15 is subjected to a mesa etchingprocess to expose the GaN buffer layer 1203, and an n-side electrode1211 is provided on a terrace surface of the GaN buffer layer 1203 thusexposed as a result of the mesa etching.

In the structure of FIG. 15, the electric current and optical radiationare confined in the ridge structure, and the laser diode forms a ridgelaser diode.

In the present embodiment, the layered structure of FIG. 15 was achievedin a single MOCVD apparatus while using TMG, TMA ant TMI for the sourceof the group III elements and NH₃ and DMHy for the source of the group Velements. In the present embodiment, there is provided a growthinterruption process during the growth process of the lower GaN opticalwaveguide layer 1205.

During the growth interruption process, the growth chamber is purged bythe carrier gas in the state that the substrate is held in the growthchamber. By purging the growth chamber by the carrier gas, theconcentration of the residual Al species in the growth chamber isreduced efficiently.

In the construction of FIG. 15, it should be noted that the InGaNquantum well layer is grown at a relatively low temperature as comparedwith the AlGaN cladding layer 1204 or GaN optical waveguide layer 1205.Thus, the InGaN quantum well layer tends to incorporate oxygen impuritytherein. However, the growth interruption process conducted prior to thegrowth of the InGaN/GaAs active layer 1206 is effective for suppressingthe oxygen being incorporated into the InGaN quantum well layer in theform coupled with Al.

With this, it becomes possible to provide a blue laser diode having areduced threshold current.

It should be noted that the present invention is effective also in thecase the active layer is any of GaNAs, GaPN, GaNPAs, GaInNAs, GaInNP,GaNAsSb, GaInNAsSb and the like.

[Tenth Mode of Invention]

As noted previously, the MBE process is not a process suitable for massproduction of a laser diode, although it is possible to obtain a veryhigh quality crystals.

In the investigation constituting the foundation of the presentinvention, the inventors have found in fact that a very high GaInNAscrystal is obtained when using an MBE process.

It should be noted that the system of GaInNAs is characterized by a verystrong immiscibility and a non-equilibrium growth such as alow-temperature growth is necessary forming a layer of GaInNAs. In thecase of the MOCVD process, it is necessary to heat the substrate to acertain temperature such that there is caused a thermal decomposition ofthe source gases. Contrary to the MOCVD process, it is possible toreduce the deposition temperature by about 100° C. by using the MBEprocess. Further, there occurs no problem of degradation of crystalquality of the GaInNAs layer in view of absence of impurity such as C(carbon) or H (hydrogen).

In the case of forming a surface-emission laser diode, it is necessaryto form a pair of semiconductor multilayer reflectors such that theactive region of the laser diode is sandwiched vertically by theforegoing semiconductor multilayer reflectors. Thus, there can be a casein which the total thickness of the surface-emission laser diode, tunedto the wavelength of the 1.3 μm band, can exceed 10 μm.

In such a surface-emission laser diode, the thickness of the activeregion is very small (10% or less of the total thickness), and most partof the surface-emission layer is formed of the layers constituting themultilayer reflectors. It should be noted that each semiconductor layerconstituting the low refractive index layer or the high refractive indexlayer of the distributed Bragg reflector has an optical thickness ofone-quarter of the laser oscillation wavelength (λ/4 thickness), and thehigh refractive index layer and the low refractive index layer arerepeated 20–40 times.

In the case of the surface-emission laser diode constructed on a GaAssubstrate, the semiconductor multilayer reflector is formed of thematerials of the AlGaAs system and the Al concentration is changedbetween the high refractive index layer and the low refractive indexlayer. In such a structure, it is noted that the multilayer reflector ofthe p-type has a larger resistance as compared with the multilayerreflector of the n-type due to the existence of hetero barrier formed atthe interface between the high refractive index layer and the lowrefractive index layer. In order to suppress the formation of the heterobarrier and to reduce the resistance, it is necessary to provide anintermediate layer of intermediate refractive index between the highrefractive index layer and the low refractive index layer. Otherwise,driving of the surface-emission laser diode becomes difficult due to theresistance of the multilayer reflector particularly at the p-type side.

Thus, in the case of a surface-emission laser diode, it is necessary togrow one hundred or more semiconductor layers of different compositions,while the number of the semiconductor layers increases further when theforegoing intermediate layers are provided between the low refractiveindex layer and high refractive index layer in the multilayerreflectors. Further, the process of forming such a multilayer reflectorrequires an instantaneous change of composition.

In view of the foregoing, the use of MBE process is not suited for theprocess of forming the multilayer reflector. In the MBE process, inwhich the composition of the semiconductor layer is controlled bycontrolling the temperature of the molecular beam cells, instantaneouschange of semiconductor composition by way of temperature change of themolecular beam cell is difficult. Further, in the case of the MBEprocess, it is difficult to increase the supply rate of the sourcematerial because of the reason explained before, and the growth rate isat best in the order of 1 μm/h. This means that it takes at least 10hours for obtain a layer of 10 μm thickness.

In the case of the MOCVD process, on the other hand, it is possible tochange the composition of the semiconductor layers by controlling thesupply rate of the source gases. As it does not require high vacuum asin the case of the MBE process, a large throughput such as 3 μm/h isachieved easily. Thus, it is concluded that the MOCVD process is mostsuitable for the formation of the semiconductor multilayer reflector.

In the case the nitrogen-containing active layer is grown by an MOCVDprocess on an Al-containing semiconductor layer grown by an MOCVDprocess, there occurs a contamination of the nitrogen-containing activelayer by the residual Al species and hence oxygen coupled with the Alspecies as explained before.

FIG. 16 shows the nitrogen concentration in a semiconductor layer as afunction of the mole ratio of DMHy with regard to the group V source(PH₃ and DMHy) for the case a GaInP layer and an AlGaInP layer are grownby an MOCVD process. The growth of the AlGaInP layer was conducted at700° C. while the growth of the GaInP layer was conducted at 650° C.

As can be seen from FIG. 16, the nitrogen concentration increases withincreasing proportion of DMHy in the group V source in the case of theGaInP layer (GaInNP layer), while a very large amount of nitrogen isincorporated when there is Al in the semiconductor layer as in the caseof the AlGaInP layer (AlGaInNP layer).

The result of FIG. 16 thus clearly shows the strong affinity between Aland nitrogen. As Al has also a very strong affinity with oxygen, oxygenis also incorporated into the nitrogen-containing layer such as theAlGaInNP layer together with Al in the form coupled with Al. Thus, asnoted before, water contained in the nitrogen compound source such asDMHy as impurity reacts with the residual Al species remaining in thegrowth chamber after growth of the Al-containing layer and isincorporated into the nitrogen-containing active layer.

Thus, in the tenth mode, the present invention provides a method offabricating a surface-emission laser diode, said laser diode comprising:an active region containing at least one active layer for causingoptical emission; and upper and lower reflectors vertically sandwichingsaid active region, said active layer containing Ga, In, nitrogen and Asas major components, one of said upper and lower reflectors being ap-type semiconductor reflector, at least said p-type semiconductorreflector including a semiconductor distributed Bragg reflector in whichthere occurs a periodic change of refractive index, said methodcomprising the steps of:

-   -   forming said active layer by an MBE process; and    -   forming at least said p-type semiconductor reflector by an MOCVD        process.

The n-side semiconductor reflector may also be grown by an MOCVDprocess.

With this, it becomes possible to form a low-resistance multilayerreflector easily while simultaneously achieving a high crystal qualityfor the GaInNAs active layer.

According to such a process, the thickness of the semiconductor layergrown by the MBE process is small (1 μm or less). Thus, the operationalload of the evacuation system of the MBE apparatus is held minimum andthe problem of frequent maintenance of the MBE apparatus is avoided.Further, the duration of the process for forming the surface-emissionlaser diode is reduced as compared with the conventional case in whichthe entire semiconductor layers are formed by the MBE process.

As the resistance of the semiconductor multilayer reflector of then-side is easily reduced by merely depositing the high refractive indexlayer and the low refractive index layer alternately and by setting thecarrier density to the level of about 1×10¹⁸ cm⁻³, it is not mandatoryto form the n-side multilayer reflector by the MOCVD process. Only thep-side multilayer reflector has to be grown by the MOCVD process.

[Eleventh Mode of Invention]

In an eleventh mode, the present invention provides a fabricationprocess a surface-emission laser diode comprising: an active regioncontaining at least one active layer for causing optical emission; andupper and lower reflectors vertically sandwiching said active region,said active layer containing Ga, In, nitrogen and As as majorcomponents, at least said lower reflector including a semiconductordistributed Bragg reflector in which there occurs a periodic change ofrefractive index, said process comprising the steps of:

-   -   forming said lower semiconductor distributed Bragg reflector in        any of an MOCVD growth chamber or in an MBE growth chamber; and    -   forming said active region in another MOCVD growth chamber.

As explained in detail with reference to the first through ninth modesof the invention, there exists a very strong affinity between Al andnitrogen, and Al is easily incorporated into the GaInNAs active layerwhen there remains residual Al species in the growth chamber. Togetherwith Al, oxygen is incorporated also in to the GaInNAs active layer inthe form coupled with Al, and the oxygen impurity thus incorporatedbecome the cause of deterioration of the efficiency of optical emission.

Thus, the present mode of the invention eliminates the problem ofincorporation of Al (and oxygen) into the active region of thesurface-emission laser diode, by changing the growth chamber whenforming the active region by an MOCVD process after the lowersemiconductor multilayer reflector is formed. Here, the lowersemiconductor multilayer reflector may be formed by any of the MOCVDprocess or MBE process.

As the growth of the active region is conducted in a new chamber notcontaminated with Al, there occurs no problem of Al contamination evenwhen the growth of the nitrogen-containing active region is conducted onthe Al-containing lower semiconductor multilayer reflector formed by anMOCVD process. In the case the lower semiconductor multilayer reflectoris formed by an MBE process, there occurs no problem of Al contamination(and oxygen contamination) of the nitrogen-containing active layer.

It should be noted that the present invention is effective also in thecase the active layer is any of GaNAs, GaPN, GaNPAs, GaInNAs, GaInNP,GaNAsSb, GaInNAsSb and the like.

[Twelfth Mode of Invention]

In a twelfth mode, the present invention provides a fabrication processof a surface-emission laser diode comprising: an active regioncontaining at least one active layer for causing optical emission; andupper and lower reflectors vertically sandwiching said active region,said active layer containing Ga, In, nitrogen and As as majorcomponents, at least one of said upper and lower reflectors including asemiconductor distributed Bragg reflector in which there occurs aperiodic change of refractive index, said process comprising the stepsof:

-   -   forming said semiconductor distributed Bragg reflector in a        first MOCVD growth chamber; and    -   forming said active region in a second MOCVD growth chamber.

In the case both of the upper and lower reflectors are formed of thesemiconductor distributed Bragg reflector, they are grown in the firstMOCVD growth chamber and the active layer is grown in the second MOCVDgrowth chamber. In the case only the lower multilayer reflector isformed of the distributed Bragg reflector, it is grown in the firstMOCVD growth chamber and the active layer is grown in the second MOCVDgrowth chamber.

According to the present invention, the multilayer reflector containingAl and the active layer containing nitrogen are grown in separate growthchambers. Thus, the growth of the active layer can be achieved in theenvironment not contaminated with Al and the problem of contamination ofthe nitrogen-containing active layer with Al and hence oxygen iseffectively and successfully suppressed. Thereby the degradation ofcrystal quality of the active layer is eliminated and the laser diodeoscillates with a low threshold current.

<Embodiment 5>

FIG. 17 shows the construction of a surface-emission laser diodeaccording to another embodiment of the present invention.

Referring to FIG. 17, the surface-emission laser diode is formed on a(001)-oriented GaAs substrate 140 of n-type having a size of 2 inches,and includes a n-type semiconductor distributed Bragg reflector 141formed on the GaAs substrate 140 with alternate repetition of an n-typeAlGaAs layer having a composition represented as AlxGa1-xAs (x=0.9) andan n-type GaAs layer each having an optical thickness of one-quarter ofthe laser oscillation wavelength of the laser diode, wherein the AlGaAslayer and the GaAs layer are repeated 35 times.

On the distributed Bragg reflector 141 thus formed, there is provided aspacer layer 142 of undoped GaAs, and a multiple quantum well activelayer 143 is formed on the spacer layer, wherein the multiple quantumwell active layer 143 includes three quantum well layers of GaInNAs eachhaving a composition of Ga_(0.63)In_(0.37)N_(0.005)As_(0.995) separatedfrom each other by a GaAs barrier layer having a thickness of 15 nm.Further, another spacer layer 144 of undoped GaAs is provided on themultiple quantum well active layer 143.

On the spacer layer 144, there is provided an upper reflector 145 ofp-type semiconductor distributed Bragg reflector, wherein the reflector145 includes a selective oxidation layer 145 ₁ of p-type AlAs having athickness of 30 nm. The selective oxidation layer 145 ₁ forms a part ofa low refractive index layer located at the bottom part of the reflector145 with an optical thickness of 3λ/4 together with a pair of p-typeAlxGa1-xAs layers (x=0.9) each having an optical thickness of λ/4–15 nmand provided above and below the layer 145 ₁. On the foregoing lowrefractive index layer of the 3λ/4 thickness, there is provided ahigh-refractive index layer of GaAs with a thickness of λ/4, and thus,there is formed a refractive index change of one period. Further, ap-type AlxGa1-xAs (x=0.9) layer and a p-type GaAs layer are repeatedalternately each with an optical thickness of λ/4 for 25 times to formthe foregoing distributed Bragg reflector 145.

It should be noted that an uppermost GaAs layer 145 ₂ of the distributedBragg reflector 145 functions also as a contact layer for achieving anohmic contact with an electrode.

In the structure of FIG. 17, the quantum well layer 143 has a thicknessof 7 nm and accumulates a compressive strain of about 2.5% (high strain)with respect to the GaAs substrate 140.

In the present embodiment, the growth of the semiconductor layersconstituting the layered structure of FIG. 17 is conducted in a growthapparatus represented in FIG. 18. In FIG. 18, those parts explainedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

Referring to FIG. 18, the growth apparatus used in the presentembodiment includes the MOCVD chamber 12 and the MBE chamber 21 coupledwith each other by a vacuum transportation path 22 including a wafertransportation chamber XT.

In the growth apparatus of FIG. 18, the load/unload chamber 11 isprovided on the wafer transportation chamber XT, and the substrate S istransported between the chambers 12 and 21 via the wafer transportationchamber XT.

Thus, when forming the GaInNAs active layer 143, the substrate 140 istransported to the MBE chamber 21, while when forming the multilayerreflector 141 or 145, the substrate 140 is transported to the MOCVDchamber 12. While it is possible to take out the substrate 140 to theatmospheric environment, it is more preferable to achieve thetransportation of the substrate 140 in the vacuum environment so as toavoid contact with the atmosphere and to avoid oxygen contamination ofthe growth interruption surface.

In the present embodiment, the growth of the GaInNAs active layer 145was conducted in the MBE chamber 21 while using the solid state sourceof Ga, In and As together with the nitrogen radical formed bydecomposing an N₂ gas in the RF radical cell 21C. In the MOCVD chamber12, on the other hand, TMG, TMI and AsH₃ was used for the growth of theAlGaAs layer together with an H₂ carrier gas. In the case the activelayer 145 accumulates a large strain as in the present case, it ispreferable to carry out the growth at low temperature such that there iscaused a non-equilibrium growth. In the present embodiment, the GaInNAslayer was grown at 430° C.

After the formation of the layered structure, a mesa etching process isconducted to form a mesa structure such that the mesa structure exposesthe sidewall surface of the AlAs selective oxidation layer 145 ₁. Thesidewall surface thus exposed is subjected to a selective oxidationprocess by applying a water vapor, and there is formed an AlxOy currentconfinement layer 146 as a result of the selective oxidation process.

After the selective oxidation process, a polyimide layer 147 is appliedfor planarization, and the polyimide layer 147 is removed from thesurface of the p-type contact layer. Further, a p-side electrode 149 isformed on the p-type contact layer such that the p-side electrode 149has an optical window 148 for allowing emission of the laser beam.Further, an n-side electrode 150 is formed on the bottom surface of thesubstrate 140.

It was confirmed that the surface-emission laser diode thus producedoscillates successfully at the wavelength of about 1.3 μm, while thislong laser oscillation wavelength was achieved on the GaAs substrate asa result of use of the GaInNAs active layer. As a result of formation ofthe current confinement structure by the selective oxidation process ofthe semiconductor layer 145 ₁ containing Al and As, the thresholdcurrent of the laser diode was suppressed successfully. Further, such acurrent confinement structure using the Al oxide film formed by theselective oxidation process of the Al-containing semiconductor layersuch as the AlAs layer 145 ₁, the current confinement structure isformed close to the active layer, and the spreading of the injectioncurrent after current confinement is minimized. Thus, according to thepresent invention, it becomes possible to confine the injected carriersin a narrow region not contacted with the air.

The current confinement structure using the Al oxide layer 146 has anadditional advantage of inducing a convex lens due to the reducedrefractive index of the Al oxide layer 146. As a result, the opticalradiation is confined effectively to the narrow region in which thecarriers are confined. Thereby, the threshold current of laseroscillation is reduced further.

As the current confinement structure is formed easily, the fabricationcost of the laser diode is reduced significantly.

Thus, according to the present embodiment, it becomes possible torealize a low const, low-power consumption surface-emission laser diodeoscillating at the wavelength band of 1.3 μm. In the fabricationprocess, it is possible to form the n-side multilayer reflector 141 andthe active layer 143 in the MBE chamber 21 and only the p-sidemultilayer reflector 145 is grown in the MOCVD chamber 12.

<Embodiment 6>

FIG. 19 shows the construction of an MOCVD apparatus according toanother embodiment of the present invention.

Referring to FIG. 19, the MOCVD apparatus has two MOCVD chambers 41 and42 connected with each other by the vacuum transportation path 22including the wafer transportation chamber XT, wherein there is provideda gas supply system 45 having a gas supply line 45 ₁ for supplying an Alsource gas and a gas supply line 45 ₂ for supplying a nitrogen sourcegas. The Al source gas in the gas supply line 45 ₁ is supplied to theMOCVD chamber 41 via an On/Off valve 45A and to the MOCVD chamber 42 viaan On/Off valve 45B. Further, the nitrogen source gas in the gas supplyline 452 is supplied to the MOCVD chamber 41 via an On/Off valve 45C andto the MOCVD chamber 42 via an On/Off valve 45D. Thereby, the valves45A–45D are controlled such that the Al source gas and the nitrogensource gas are never supplied to the same MOCVD chamber simultaneously.

In the apparatus of FIG. 19, the MOCVD chamber 41 includes therein avertical reactor while the MOCVD chamber 42 includes therein a lateralreactor. The growth of the Al-containing reflector such as the lowerreflector 141 and the upper reflector 145 is conducted in the firstMOCVD chamber 41, while the growth of the GaInNAs active layer 143 isconducted in the second MOCVD chamber 42.

For the growth of the GaInNAs active layer 143 in the MOCVD chamber 42,TMG, TMI and AsH₃ may be used together with DMHy. In this case, thesesource materials are supplied to the MOCVD chamber 42 with a carrier gasof H₂, and the growth of the GaInNAs active layer 143 may be conductedat the temperature of 540° C. It should be noted that DMHy decomposes atlow temperature and is suited for the low temperature growth processconducted at the temperature of 600° C. or lower as in the present casein which a highly strained layer is grown by a low-temperaturenon-equilibrium process.

It should be noted that the vertical reactor used in the MOCVD chamber41 is characterized by excellent uniformity and is suited for growingthe multilayer reflectors. On the other hand, the lateral reactor usedin the MOCVD growth chamber 42 has an advantage of forming a laminarflow and is suited for forming the GaInNAs active layer. The lateralreaction of the growth chamber 42 is further suited for the growth ofthe GaInAs active layer in view of the existence of upstream side anddown stream side. Thus, it is possible to decompose the source gasbefore the gas reaches the substrate.

Thus, the construction of FIG. 19 allows combination of variousdifferent types of reactors, and thus, the MOCVD apparatus of FIG. 19can be optimized for growing a layered semiconductor body as in the caseof the surface-emission layer diode by using optimum growth chamber forthe growth of respective, different semiconductor layers.

As the growth chambers are connected with each other by the vacuumtransportation path 22 also in the construction of FIG. 19, there arisesno adversary effect of growth interruption surface, and it becomespossible to grow the GaInNAs surface-emission laser diode with excellentthroughput.

In the foregoing explanation, it should be noted that the growthinterruption surface is not limited in the GaAs spacer layer. In view ofthe possibility of non-optical recombination of carriers in such agrowth interruption surface, it is more preferable to form the growthinterruption surface in the reflector, rather than forming the same inthe active region. For example, a high refractive index layer and a lowrefractive index layer in the reflector may be formed such that there isformed a growth interruption surface somewhere between the highrefractive index layer and the low refractive index layer.

In doing so, it is more preferable to form the growth interruptionsurface in the Al-free layer such as the GaAs layer in view ofpossibility of adversary effect of oxidation in the event the growthinterruption surface is formed in the Al(Ga)As layer. In such a case,there can be an adversary effect of oxidation even in the case thesubstrate is transported in the vacuum environment. In view of thepossibility of adversary effect caused in the GaInNAs layer by Al whenthe growth of the GaInNAs layer is achieved by an MOCVD process, it ispreferable to use an Al-free material such as GaxIn1-xPyAs1-y (0<x≦1,0<y≦1) for the low refractive index layer.

FIG. 20 shows an example of such a case. In FIG. 20, those partscorresponding to the parts described previously are designated by thesame reference numerals and the description thereof will be omitted.

Referring to FIG. 20, there is formed a GaInPAs layer 151 having acomposition represented as GaxIn-xPyAs1-y (0<x≦1, 0<y≦1) in the step offorming the active region but before the step of forming the GaInNAsactive layer as one of the low refractive index layers constituting thelower reflector 141. The upper reflector 145 has a constructionidentical with that of the embodiment of FIG. 18.

After the formation of the GaInPAs layer 151, there is a sufficient timebefore the growth of the GaInNAs active layer 143 is started. Thus, bycontinuing the evacuation process of the reaction chamber, it ispossible to eliminate the contamination of the GaInNAs active layer byAl or oxygen. It should be noted that this cleaning process is conductedin ordinary process, and thus, there is no increase of the processsteps. Further, such a cleaning process can be conducted efficiently bysupplying the hydrogen carrier gas and heating the susceptor in thegrowth chamber.

Most preferably, the growth of the GaInNAs active layer 143 is conductedin the growth chamber 41, which is different form the growth chamber 42used for growing the Al-containing layers.

<Embodiment 7>

FIG. 21 shows the construction of an optical transmission module inwhich the surface-emission laser diode of FIG. 17 is coupled with anoptical fiber.

Thus, in the optical transmission module of the present embodiment, alaser beam 53 emitted from the GaInNAs surface-emission laser diode 51of the 1.3 μm band is injected into a quartz glass optical fiber 52 andis transmitted. In a modification of the construction of FIG. 21, it ispossible to arrange a number of surface-emission laser diodes ofdifferent wavelengths in the form of one-dimensional or two-dimensionalarray and construct a wavelength-multiplex optical transmission system.Thereby, the transmission rate in the optical fiber 52 is increased.Further, it is possible to couple an optical fiber bundle to thesurface-emission laser diode array, such that each surface-emissionlaser diode element is coupled to a corresponding optical fiber formingthe optical fiber bundle.

Thus, by using the surface-emission laser diode of the present inventionfor the optical telecommunication, it is possible to realize a reliablelow-cost optical module. By using such a reliable and low-cost opticalmodule, it is possible to realize a reliable, low-cost opticaltelecommunication system. As the GaInNAs surface-emission laser diodehas excellent temperature characteristics and low threshold, the laserdiode produced little heat and can be used without cooling up to hightemperatures.

<Embodiment 8>

FIG. 22 shows the construction of an optical transmission/receptionmodule in which the surface-emission laser diode of FIG. 20 is combinedwith a photodiode and an optical fiber.

Referring to FIG. 22, a surface-emission laser diode 61 corresponding tothe GaInNAs surface-emission laser diode of the 1.3 μm band shown inFIG. 20 and a photodiode 62 are coupled optically with an optical fiber63. Thus, it becomes possible to realize a reliable low-cost opticaltelecommunication system. As the surface-emission laser diode of thepresent invention is characterized by small threshold current and lowdrive voltage, the laser diode can be operated with little heating andcan be used up to high temperatures without cooling.

Particularly, by combining with a fluorinated plastic optical fiber(OPF) having a transmission band at the 1.3 μm band, a very low costoptical module is realized in view of the large diameter of the opticalfiber.

It should be noted that the optical telecommunication realized by thesurface-emission laser diode is not limited to the one for long-distancetelecommunication but also includes short to medium distance opticaltelecommunication such as data transfer between computers as in the caseof optical LAN, date transfer between circuit boards, data transferbetween LSIs on a circuit board, data transfer inside an LSI, and thelike.

By using the surface-emission laser diode of the present invention foroptical interconnection inside a computer system, the bottleneck problemof data transfer rate, encountered in the case conventional electricwiring has been used, is successfully overcome, and a super fastcomputer system becomes possible.

Further, by connecting plural computer systems with each other by usingthe optical module of the present invention, it becomes possible toconstruct a super fast network system. It should be noted that the powerconsumption of the surface-emission laser diode of the present inventionis drastically reduced as compared with the conventional edge-emissionlaser diodes, and thus, the surface-emission laser diode of the presentinvention is particularly suited for constructing a two-dimensionallaser diode array.

As explained heretofore, the surface-emission laser diode using theGaInNAs active layer has various advantageous features such as:possibility of using the Al(Ga)As/(Al)GaAs semiconductor distributedBragg reflector of which use is established already in the art of the0.85 μm band surface-emission laser diode; possibility of using thecurrent confinement structure formed by the selective oxidation processof AlAs; improvement of crystal quality of the GaInNAs active layeraccording by eliminating the Al and oxygen contamination as explainedbefore; decrease of resistance of the multilayer reflector; improvementof crystal quality and controllability of composition of thesemiconductor layers forming the multilayer mirror, and the like. Thus,the present invention provides a practical surface-emission laser diodeoperable in the wavelength band of 1.3 μm. The surface-emission laserdiode of the present invention can eliminate the cooling device, andprovides the possibility of constructing various low-cost opticaltelecommunication systems including optical fiber telecommunicationsystems and optical interconnection systems.

<Embodiment 9>

FIG. 23 shows the construction of a surface-emission laser diodeaccording to another embodiment of the present invention, wherein thoseparts corresponding to the parts described previously are designated bythe same reference numerals and the description thereof will be omitted.

Referring to FIG. 23, the laser diode has a structure similar to that ofthe device of FIG. 20, except that the GaInPAs layer 151 is providedinside the optical cavity. Further, the optical cavity of the presentembodiment forms a one-lambda cavity.

More specifically, the optical cavity includes three GaInNAs quantumwell layers 143 interposed with GaAs barrier layers, wherein there areprovided upper and lower spacer layers 152 of GaAs above and below thethree-quantum well structure formed of the three GaInNAs quantum welllayers 143, and the GaInPAs layers 151 are provided outside the GaAsspacer layers 152 as second spacer layers. As the GaInPAs layers 151have a bandgap larger than that of GaAs, the carriers are actuallyinjected into the region inside the GaAs layers 152, and an effectsimilar to the device of FIG. 20 is achieved.

In the present embodiment, the growth interruption for changing thegrowth chamber is conducted during the growth of the GaInPAs layer 151,and thus, the growth interruption surface is formed inside the GaInPAslayer 151. However, this growth interruption can be made also during thegrowth of a GaAs layer, which is provided between the GaInAsP layer 151and an Al-containing layer.

When the MOCVD apparatus of FIG. 18 is used for the fabrication of thedevice of FIG. 23, the n-type distributed Bragg reflector 141 may beformed in the MBE growth chamber 21. In this case, thenitrogen-containing active layer 143 and the p-type upper reflector 145can be grown in the MOCVD chamber 12. In this case, there is only onechange of the growth chamber and the efficiency of production of thelaser diode is improved. Once the substrate is moved to the growthchamber 12 and the nitrogen-containing active layer 143 is formed, theremaining process can be conduced subsequently in the same growthchamber 12. Even in such a case, no contamination of thenitrogen-containing active layer 143 occurs. Further, the resistance ofthe p-type reflector 145 is reduced.

[Thirteenth Mode of Invention]

A refining process of hydrazine is shown in a Japanese Laid-Open PatentApplication 7-230953 official gazette and Japanese Laid-Open PatentApplication 9-251957 official gazette.

Thus, the vapor phase growth method of a

III-group V semiconductor material in which the water content inhydrazine is 100 weight ppm or less is shown in Japanese Laid-OpenPatent Application 7-230953. Particularly, an example of growing anInGaAlN film with an MOVPE process is shown, in which commerciallyavailable hydrazine is distilled in a nitrogen atmosphere afterdehydration with calcium carbide.

Also, the process of making an InGaAlN film by an MOCVD process thatuses, as the nitrogen source, hydrazine and ammonia is shown in JapaneseLaid-Open Patent Application 9-251957. It distills commerciallyavailable hydrazine in a nitrogen atmosphere after dehydration withcalcium carbide and growth of an InGaAlN film is made with an MOVPEprocess.

However, removal of water content or alcohol is not sufficient, even ifpurification is made with the conventional method as shown in JapaneseLaid-Open Patent Application 7-230953 or Japanese Laid-Open PatentApplication 9-251957, for the improvement of the crystal quality of thesemiconductor film in a device that uses the material system of theIII-group V semiconductor material containing nitrogen (N).

Accordingly and it was found out that it is necessary to remove watercontent or alcohol from the nitrogen source material. Thereupon, in thismode of the present invention, there is an objective that the impurityis removed sufficiently from the nitrogen source material and to providethe method of producing the group III–V compound semiconductor filmcontaining nitrogen (N) of excellent crystal quality and containinglittle impurities.

FIG. 24 shows an example of the semiconductor film growth apparatusaccording to the present invention.

FIG. 24 is referred to. The semiconductor film growth apparatus isconstituted from a reaction chamber 61 for growing a III–V groupcompound semiconductor film containing nitrogen (N) on a substrate, agroup III source 62 for supplying a group III source material to thereaction chamber 61, a nitrogen source 64, a purifying unit 65 forsupplying the nitrogen source material to the reaction chamber 61 afterpurification by removing impurities from the nitrogen source, which is anitrogen compound from the nitrogen source 64, and a gas evacuation unit66.

A MOCVD apparatuses, A MOMBE apparatuses, A CBE apparatus, and the like,are examples of such a growth apparatus. Thus, It is possible to carryout a growth method such as the MOCVD process, MOMBE process, CBEprocess, etc. inside the reaction chamber 61.

In FIG. 24, it is also possible to use B, Al, Ga, In, Tl for the groupIII element (group III source material) and can use P, As, Sb, Bi otherthan N for the group V element (group V source material). As for thenitrogen compound, it is possible to use amines and the like such asNH₂R, NHR₂, NR₃ (R is an alkyl group or aryl group) in addition to NH₃,hydrazine and the like, It is desirable, however, that the hydrazine orthe like is contained in the nitrogen compound at least.

In more detail, NH₃ and amines are characterized by high decompositiontemperature and a temperature condition of 900° C. or the like, isnecessary for forming active species with sufficient concentration.Because of this, it becomes easy to occur escaping of constitutingelements from the growth film. In the case of the growth film containingIn or N, the problem of escaping of these atoms becomes distinct.Contrary to this, the decomposition temperature of hydrazines is low,and it is possible to form the active species with sufficientconcentration in the vicinity of 500° C., and the excellent growth filmis obtained easily.

Here, hydrazines are the material having the chemical formula of NR₂NR₂(R is hydrogen, alkyl group or aryl group) and include hydrazine,monomethylhydrazine, dimethylhydrazine, butylhydrazine, hydrazobenzene,and the like.

In the semiconductor growth apparatus of FIG. 24, a metallic Al or analloy containing metallic Al is disposed in the refinement chamber ofthe refining unit 65 such that the nitrogen source material (nitrogensource of a nitrogen compound) makes a contact with the metallic Al oralloy containing metallic Al in the refinement apparatus 65. Thereby,the metallic Al or the alloy containing metallic Al purifies thenitrogen source (removes the impurity), and the refined nitrogen sourceis supplied to the reaction chamber 61. Here, the transport of thenitrogen source gas is generally achieved by a carrier gas. However, itis also possible to achieve transport by the vapor pressure of thenitrogen source gas.

Al—In, Al—Ga, Al—In—Ga, and the like, are examples of the alloycontaining metallic Al. These alloys can change the melting temperaturefrom the room temperature or the like to about the melting temperature(660° C.) of Al. For example, the one having the weight ratio of GaInAlof 100:10:1.8 is a liquid at room temperature.

In the semiconductor film growth apparatus of the construction of FIG.24, metallic Al or the alloy containing metallic Al is placed in advancein the refining chamber of the refining unit 65. Thereafter, thenitrogen source material (nitrogen source gas) is introduced into therefining chamber of refining unit 65 by a carrier gas of H₂, He, Ar, N₂and the like, or by the vapor pressure of the nitrogen source materialitself. After refinement by contacting with the metallic Al or the alloycontaining metallic Al, the nitrogen source material is transported tothe reaction chamber 61.

At the same time, the vapor of the metal-organic compound, hydride orsimple substance, of the constituting element of the group III–Vcompound semiconductor film including nitrogen (N) is introduced intothe reaction chamber 61, and a group III–V compound semiconductor filmcontaining nitrogen is caused grow on the substrate.

In the refining unit 65, it should be noted that metal Al reacts easilywith water or alcohol when contacted with the nitrogen source gas of anitrogen compound because of the large negative value of free energy offormation of the oxide. In this way, the purity of the nitrogen sourcematerial can be improved.

Thus, in the present invention, the nitrogen source material of anitrogen compound is contacted to metallic Al or the alloy containingmetal Al and is then transported to the reaction chamber 61 for growingthe group III–V compound semiconductor film containing nitrogen. As thenitrogen source material is contacted to metallic Al, water content oralcohol and is removed from the nitrogen source gas and a nitrogensource gas of nitrogen compound from which water content or alcohol isremoved (sufficiently purified nitrogen source material) is supplied tothe reaction chamber 61. As a result, it becomes possible to obtain agroup III–V compound semiconductor film containing nitrogen and havingexcellent crystal quality characterized by little impurities.

Also, in the case at least any of hydrazines is contained in thenitrogen compound, it is possible to obtain a group III–V compoundsemiconductor film containing nitrogen with high concentration withimproved crystal quality as being characterized by the existence oflittle impurities. Thus, in the case of using hydrazines having highreactivity and is capable of providing an epitaxial growth film of highcrystal quality as the nitrogen source material, it becomes possible tosupply a high purity hydrazine, from which water content or alcohol isremoved, to the reaction chamber 61 by using the purification method ofthe present invention mentioned above. As a result, a group III–Vcompound semiconductor film containing nitrogen and is characterized bya lower impurity concentration level and higher crystal quality isobtained.

In the case the metallic Al or the alloy containing metallic Al is aliquid phase in the semiconductor film growth method of theabovementioned mode, the nitrogen source gas of a nitrogen compound ispassed through the metallic Al or the alloy containing metal Al by wayof a bubbling process and is then transported to the reaction chamber61.

FIG. 25 shows an example of the refining unit 65 that transports thenitrogen source gas of a nitrogen compound to the reaction chamber 61after bubbling through the metallic Al or the alloy containing metallicAl for the case the metallic Al or the alloy containing metallic Al isin the liquid phase (molten Al or molten Al alloy).

In the case that the metallic Al or the alloy containing metallic Al isa liquid, the nitrogen source gas passes through the liquid of themetallic Al or the alloy containing metallic Al by way of bubbling, anda large contact area is secured for the gas/liquid interface. Thereby,removal of the water content or alcohol in the nitrogen source gas isachieved efficiently and it becomes possible to obtain a high qualitygroup III–V compound semiconductor film that contains nitrogen butlittle impurities.

FIG. 25 is referred to. The refining unit 65 includes a container 65Bheld in a thermostatic bath 65A and molten Al or molten Al alloy 65C isheld in the container 65B. Further, a thermal medium 65D of air or aliquid is provided between the thermostatic bath 65A and the container65B.

Also, it is possible to use a solid phase metallic Al or the alloycontaining metallic Al in the semiconductor film growth method of thepresent invention mentioned above.

In the case the metallic Al or the alloy containing the metallic Alforms a solid phase (a solid), it is preferable that the metallic Al orthe alloy containing metal Al is in a particle state or fine particlestate or membrane state or porous state so as to increase the contactarea.

FIG. 26 shows the example of refining unit 65 that uses the pellet orfine particles of the solid state Al or the solid state Al alloy. Also,FIG. 27 shows the example of another refining unit 65 that uses pelletor fine particles of the solid state Al or the solid state Al alloy.

FIG. 26 is referred to. The refining unit 65 is formed of a container65E supplied with the nitrogen source material with a carrier gas and apurification medium 65 F of the pellet or fine particles of solid stateAl or solid state Al alloy held in the container 65E. In the example ofFIG. 27, on the other hand, the refining unit 65 is formed of acontainer 65E supplied with the nitrogen source material with a carriergas and a purification medium 65H of pellet or fine particles of thesolid state Al or the solid state Al alloy held in the container 65G.

The metallic Al or the alloy containing metallic Al of the particle formcan be produced by dropping molten metallic Al or molten alloycontaining the metallic Al molten in an inert gas on a refrigeratedmetal plate or into a refrigerated inert liquid such as a fluorinatedoil or silicone oil. Also, it is possible to produce the fine particlesof the metallic Al or the alloy containing the metallic Al can beproduced for example by evaporating the metallic Al or the alloycontaining the metallic Al in an inert gas. The metallic Al or the alloycontaining the metallic Al can be formed in the form of a film by avacuum evaporation deposition process or sputtering process. Also, it ispossible to produce the film of the metallic Al or the alloy containingmetallic Al by an evaporation deposition process or sputtering processwhile rotating the particle of glass or ceramic. In this case, the glassor ceramic may form a porous body.

In the case the metallic Al or the alloy containing the metallic Al isin a particle state or fine particle state or film state or porous body,a large contact area of the metallic Al or the alloy containing themetallic Al to the nitrogen source gas is secured, and it is possible toremove the water content and the alcohol content from the nitrogensource gas effectively. As a result, there remain little impurities andone can obtain a high quality group III–V compound semiconductor filmcontaining nitrogen.

Furthermore, it is possible to provide a reaction excitation means inthe reaction chamber 61 in the construction of FIG. 24, such as heatingmeans heating the substrate or plasma generation means exciting thereaction of the source material or electron beam source means etc. forexciting the reaction. In the case that the material is liquid, it ispreferable to introduce an inert gas into the reaction chamber 61 by abubbling as a careers gas. Also, it is possible to heat the sourcematerial, in the case the source material is a solid body, so as toevaporate toward the substrate by way of sublimation or evaporation andtransport it to reaction chamber 61 by the careers gas. Also, a vacuumpump is connected to the gas exhaust part 66 in the case of growing thefilm under low pressure or vacuum environment.

FIGS. 28 and 29 show the example of supplying the nitrogen sourcematerial by bubbling for the case the nitrogen source material is aliquid.

In the example of FIG. 28A, there is provided a first bubbler 71containing the nitrogen source material and the above-mentionedrefinement unit 65 is provided between this first bubbler 71 and thereaction chamber 61. Thereby, the nitrogen material gas is transportedto the reaction chamber 61 with an H2 gas etc. as a career gas.

In the example of FIG. 29, there is provided a second bubbler 73 inconnection with the refinement unit 65 in the upstream side of the firstbubbler 72, and the nitrogen source material (N source) in the secondbubbler 73 is stored in the first bubbler 72 while conducting therefining process. By bubbling the first bubbler 72, the refined nitrogenmaterial is transported into the reaction chamber 61.

It should be noted that the use or no use, location or arrangement ofthe mass flux controllers (MFC), valves, pressure gauges, and the like,is not limited to the example of FIGS. 28 and 29. Also, it is desirableto provide a dust filter to the line between the refinement unit 65 andthe reaction chamber 61 so as to prevent the oxides formed in therefinement unit 65 being transported to the reaction chamber 1 as adust.

Thus, according to the present invention, there is provided ahigh-quality nitrogen-containing group III–V compound semiconductor filmcontaining little impurity. The semiconductor device using the nitrogencontaining III–V group compound semiconductor film as a constituent filmis not limited to a light-emitting device but includes alsophotodetection devices, solar cells and electrons devices such as FETs,bipolar transistor transistors, and the like.

In the present invention, it is also possible to use a GaN material asthe above-mentioned nitrogen containing group III–V compoundsemiconductor film. Here, the GaN material includes GaN, GaInN, AlGaInN,AlGaN, GaPN, GaInPN, AlGaInPN, AlGaPN, BGaN, BGaInN, BAlGaInN, BAlGaN,GaNSb, GaInNSb, AlGaInNSb, AlGaNSb, and the like.

These GaN materials have a band gap energy corresponding to thewavelength of far ultraviolet range to the visibility range. Especially,GaN, GaInN, AlGaInN and AlGaN can be grown epitaxially on a selectivelygrown GaN film in addition to the single crystal films of α-Al2O3,β-SiC, h-ZnO, and the like.

The GaInNAs system material film can be formed by reacting the hydridesource material, organic metal compound source materials or halogenatedsource material of Ga, In, Al, B and P with the nitrogen source materialthat passed through the refinement unit 65.

FIG. 30 shows an example of causing an epitaxial growth of a GaNmaterial by the MOCVD apparatus. In the drawing, those parts explainedpreviously are given with the same the same reference numerals and thedescription thereof will be omitted.

The example of FIG. 30 is in the construction to grown the epitaxialgrowth films of GaN, GaInN, AlGaInN and AlGaN. Thus, in the example ofFIG. 30, there is provided a susceptor having a heating system in thereaction chamber 61 evacuated by a vacuum pump 66, and there areprovided lines for supplying a high purity H2 gas from the hydrogen gasrefinement unit 13 as a carrier gas together with the organic metal suchas Ga (CH₃)₃(TMG), Al(CH₃)₃: (TMA), In(CH₃)₃(TMI) and AsH₃ or PH₃ to thereaction chamber 61. Further, lines for the dopant gas such as SiH₄ andZn(CH₃)₂(DMZn) are provided. Furthermore, there is provided a gascylinder 91 of NH₃ gas, and the refinement unit 65 of the nitrogensource material is provided between the gas cylinder 91 and the reactionchamber 61.

By using the MOCVD device of FIG. 30, it becomes possible to obtain ahigh quality GaN compound semiconductor film containing little impurityas a result of supplying the high purity nitrogen source material fromwhich moisture and alcohol are removed to the reaction chamber 61.

It should be noted that the device using the GaN compound semiconductorfilm is not limited to the above-mentioned semiconductor light-emittingdevice but also includes photodetection devices, solar cells andelectron devices such as FETs and bipolar transistor transistors.

Also, a GaInNAs material can be formed in the present invention as thegroup III–V compound semiconductor film containing nitrogen.

Here, GaNAs, GaInNAs, GaInAsSb, GaInNP, GaNP, GaNAsSb, GaInNAsSb, InNAs,InNPAs etc. are the examples of the GaInNAs material.

It should be noted that the light-emitting device that uses the GaInNAsmaterial for the active layer can be used successfully in combinationwith the quartz optical fiber because of the long wavelength band of 1.1μm or more, in addition to the advantageous features of excellenttemperature characteristic. Therefore, it is conceivable that suchlight-emitting devices would become an indispensable element in opticaltelecommunication systems or optical interconnection between computers,between chips inside a chip, or in optical computing.

Also the GaInNAs material can adjust the composition thereof so as toachieve lattice matching with GaAs. Thus, the material of the GaInNAssystem can cause an epitaxial growth on a GaAs substrate.

Such a GaInNAs film can be formed by causing a reaction in the hydride,organic metal compound, or halogenated material of Ga, In, As, Sb and Pwith the nitrogen source material passed through the refinement unit 65.

FIG. 31 shows the example of growing an epitaxial film of the GaInNAssystem with the MOCVD device. In FIG. 31, those parts explainedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

FIG. 31 is referred to. In the illustrated example, it should be notedthat the supply lines of the Al source material and the P sourcematerial are added so as to be able to grow the epitaxial films ofGaAlAs, AlAs, and GaInP.

In the example of FIG. 31, the lines for supplying AsH₃, PH₃ and thehydride of organic metals such as TMG, TMA and TMI to the reactionchamber 61 together with the career gas of high purity H₂ gas areprovided, wherein the reaction chamber is evacuated by the vacuum pump66 and is provided with a susceptor that can heat the substrate thereon.Furthermore, the lines of doping gas such as SeH₂ and Zn(CH₃)₂(DMZn) areprovided. Furthermore, there is provided a first bubbler 92 containingthe nitrogen material source, and there is provided, between the firstbubbler 92 and the reaction chamber 61, the nitrogen source refinementunit 65 of the present invention. Thereby, the H₂ careers gas is used totransport the nitrogen source gas into the reaction chamber 61.

By using the MOCVD apparatus of FIG. 31, it becomes possible to supplythe high purity nitrogen source gas, from which the moisture and alcoholare removed, to the reaction chamber 61. As a result, it becomespossible to obtain a high quality GaInNAs compound semiconductor filmcontaining little impurity.

It should be noted that the device that uses the GaInNAs compoundsemiconductor film as a constituent film is not limited to theabove-mentioned semiconductor light-emitting device but also includesphotodetection devices, solar cells, and also electron devices such asFETs and bipolar transistors.

More specifically, it is possible to produce a laser diode by using theabove semiconductor film growth method and also the semiconductor filmgrowth apparatus.

For example, it is possible to form the group III–V compoundsemiconductor film containing nitrogen (N) with the GaN material. Inthis case, a laser diode having the active layer of the GaN material canbe formed.

Such a laser diode includes the laser diodes that includes the growthfilm of GaN, GaInN, AlGaInN, AlGaN, GaPN, GaInPN, AlGaInPN, AlGaPN,BGaN, BGaInN, BAlGaInN, BAlGaN, GaNSb, GaInNSb, AlGaInNSb, AlGaNSb, andthe like, in the active layer.

The laser diode is divided generally into an edge emission type deviceand a surface emission type device.

In the case of the edge-emission laser diode, there are types such assingle heterojunction type, double heterojunction type, separateconfinement junction (SCH) type, and multiple quantum well structure(MQW) type. In terms of the type of the cavity, there are types such asFabri-Perot (FP) type, distributed-feedback (DFB) type, distributedBragg reflector (DBR) type.

As explained in the previous mode, a surface emission laser diode formsthe laser cavity in vertical direction to the substrate, and emits theoptical beam in the direction perpendicular to the substrate. In thesurface emission laser diode, there are provided high-reflectancereflectors such as a semiconductor multilayer reflector, a dielectricmultilayer reflector or a metal reflector on the surface of thesubstrate, and the active layer is provided between these reflectors.Further, a spacer layer is provided between the active layer and any ofthe two reflectors. Further, in the case of a surface emission laserdiode, there are often the case in which a current confinement structureis provided so as to confine the current path in the vicinity of theactive layer for reducing the threshold current and ensuring asingle-mode oscillation and further to prevent non-optical recombinationat the sidewall.

As explained before, a surface-emission laser diode can be integrated inthe form of a two-dimensional array. Further, it has a feature in that,because of relatively narrow angle of divergence of output optical beam(about 10 degrees), coupling with an optical fiber is easy and also theinspection of the device is easy. Therefore, it is thought that thedevice is particularly suited to construct an optical transmissionmodule (optical interconnection device) of parallel-transmission type.The immediate application of the optical interconnection apparatus isshort distance optical fiber telecommunication in addition to theparallel connection of computers or connection between the boards. Onthe other hand, application to large-scale computer network is alsoexpected in the future.

FIG. 32 shows an example of the edge-emission type laser diode of theSCH structure that uses an InGaN film as the active layer.

FIG. 13 is referred to. The edge-emission type laser diode has a layeredstructure in which a buffer GaN layer 302, a foundation n-type GaN layer303, an n-type AlGaN cladding layer 304, n-type GaN guide layer 305, anInGaN active layer 306, a p-type GaN guide layer 307, a p-type AlGaNcladding layer 308 and a p-type GaN contact layer 309 are laminatedconsecutively on a substrate 301 of a single crystal of α-Al2O3, β-SiC,h-ZnO, and the like, or of a selectively grown GaN film. Further, ap-type electrode 310 is formed on the p-type GaN contact layer 309, andan n-type electrode 311 is formed on the lower n-type GaN layer 303.

In the illustrated example, there is formed a cavity by dry etchingprocess, and the like, in parallel with the film surface.

In the edge-emission laser diode of FIG. 32, there is caused an opticalemission in the active layer 306 as a result of injection of holes andelectrons respectively into the p-type cladding layer 308 and the n-typecladding layer 304.

Also, FIG. 33 shows the example of the surface-emission laser diode thatuses a quantum well structure (QW) for the active layer in which anInGaN film is used as the well layer and AlGaN is used as the barrierlayer.

FIG. 33 is referred to. The surface emission laser diode has a layeredstructure in which an AlN buffer layer 402, a GaN buffer layer 403, asemiconductor multilayer reflector) lower semiconductor distributedBragg reflector 404 in which an AlN/GaN structure is repeated more than20 times, an n-type GaN contact layer 405, an n-type GaN spacer layer406, an InGaN/AlGaN quantum well (QW active layer 407, a p-type GaNspacer layer 408, a p-type GaN contact layer 409, and a semiconductormultilayer reflector (upper semiconductor distributed Bragg reflector)410, in which the AlN/GaN structure is repeated about 20 times, areformed consecutively on a substrate 401 of α-Al2O3, β-SiC or h-ZnOsingle crystal or a selectively grown GaN film.

In the example of FIG. 33, a current confinement part 411 is provided inthe vicinity of the active layer 407 by forming an insulating region byway of ion injection of proton or oxygen. Further, a p side electrode412 is formed on the above-mentioned p-type contact layer 409 and alsoan n side electrode 413 is formed on the above-mentioned n-type contactlayer 405.

Like this, the device of FIG. 33 is a surface-emission type device thathas a cavity structure in a vertical direction of the epitaxial films.

In the surface-emission laser diode of FIG. 14, there occurs opticalemission in the active layer 407 as a result of injection of holes andelectrons into the above-mentioned p-type semiconductor multilayerreflector 410 and the n-type semiconductor multilayer reflector 404respectively.

Thus, when forming the group III–V compound semiconductor filmcontaining nitrogen with the GaN material and producing a laser diodehaving the GaN material as the active layer, a laser diode constitutingfilm having a high crystal quality is obtained by contacting thenitrogen source material of a nitrogen compound with the metallic Al orthe alloy of the metallic Al for refining the nitrogen source materialand by using such a refined nitrogen source material. Particularly, inthe case of the active layer including a/the GaN system material, thecrystal quality is improved by conducting such a refinement process.Furthermore, an oscillation wavelength of the visibility wavelength toultraviolet wavelength region is achieved as a result of use of the GaNmaterial, and a wide application development is expected.

Accordingly, a laser diode having an oscillation wavelength of visibleto ultraviolet wavelength range is obtained with the features of lowthreshold current, high radiation efficiency, high reliability and longlifetime.

As another example of the laser diode, it is possible to construct alaser diode by using the GaN material for the group III–V compoundsemiconductor film containing nitrogen (N) and construct a laser diodehaving a GaInNAs material for the active layer.

For example such a laser diode may be a laser diode having the growthfilm of GaNAs, GaInNAs, GaInAsSb, GaInNP, GaNP, GaNAsSb, GaInNAsSb,InNAs, InNPAs etc. as the active layer.

FIG. 34 shows an example of the edge-emission laser diode having the SCHtype structure in which a GaInNAs film is used as the active layer.

FIG. 34 is referred to. The edge-emission laser diode includes an n-typecladding layer 502 of n-type AlGaAs or n-type GaInP, a guide layer 503of GaAs or GaInP, an active layer 504 of GaInNAs, a guide layer 505 ofGaAs or GaInP, a p-type cladding layer 506 of p-type AlGaAs or p-typeGaInP laminated consecutively on a GaAs single crystal substrate 501,and a p-side electrode (stripe electrode) 507 is formed on the p-typecladding layer 506 and an n-side electrode (lower electrode film) 508 isformed on the rear surface of the substrate 501. Further, there isformed to a cavity operating parallel to the epitaxial films is formedby a cleaving process.

In the edge-emission laser diode of FIG. 34, optical emission is causedin the active layer 504 by injecting holes and electrons into the p-typecladding layer 506 and n-type cladding layer 502 respectively.

FIGS. 35A and 35B show an example of the surface-emission laser diodethat has a quantum well structure (QW) active layer in which a GaInNAsfilm is used for the quantum well layer and the GaAs layer as a barrierlayer.

FIGS. 35A and 35B are referred to. The surface-emission laser diodeincludes an n-type semiconductor multilayer film 602 in which an n-typeGaInP/n-type GaAs structure is repeated more than 25 times, a spacerlayer 603 of n-type GaAs, n-type GaInP, n-type AlGaAs, and the like, anactive layer 604 of GaInNAs/GaAs quantum well (QW), a spacer layer 605of p-type GaAs, p-type GaInP, p-type AlGaAs, a semiconductor multilayerreflector 606 in which the p-type GaInP/p-type GaAs structure isrepeated 20 times or more, and a p-type contact layer 607 are stackedconsecutively on an n-type GaAs single crystal substrate 601.

The above-mentioned active layer 604 is formed of a GaInAs quantum wellactive layer 604 a and a GaAs barrier layer 604 b, and in the example ofFIGS. 35A and 35B, there is formed a current confinement part 608 in thevicinity of the active layer 604 by oxidizing the AlAs film to form aninsulating Al_(x)O_(y) film in the vicinity of the active layer 604 orby forming an insulating region by the ion implantation of proton oroxygen in the vicinity of the active layer 604. Further, a p-sideelectrode 609 is formed on the p-type contact layer 607 and an n-sideelectrode 610 is formed to the rear side of the substrate 601. Thereby,there is formed a surface-emission laser diode having a cavity structurevertical to the film surface.

In the surface-emission laser diode of such a construction, there isformed a radiation in the active layer 604 as a result of injection ofholes and electrons to the p-type semiconductor multilayer reflector 606and the n-type semiconductor multilayer reflector 602 respectively.

In this embodiment, too, a laser diode formed of high qualitysemiconductor films is obtained by forming the group III–V compoundsemiconductor film containing nitrogen with the GaInNAs material and byforming the active layer by the GaInNAs material, as a result of therefining of the nitrogen source material of a nitrogen compound bycontacting with the metallic Al or the alloy containing the metallic Al.By using the nitrogen source material thus refined, the crystal qualityof the active layer containing the GaInNAs material is improvedremarkably. Further, this laser diode radiates in the infrared regionsuitable for use with an optical fiber as a result of the active layercontaining the GaInNAs material. Furthermore, there is caused littlechanges of radiation characteristic with the change of temperature as aresult of excellent carrier confinement. Accordingly, an infrared laserdiode characterized by low threshold current, excellent temperaturecharacteristic, high reliability, long lifetime, and the oscillationwavelength suitable for optical telecommunication is obtained. Further,it is possible to construct the laser diode having the GaInNAs materialas the group III–V compound semiconductor film that contains nitrogenand containing the GaInNAs material in the active layer in the form of asurface-emission laser diode that includes at least one semiconductormultilayer reflector of AlxGa1-xAs/AlyGa1-yAs (0≦y<x≦1).

As the reflector of a surface-emission laser diode, a semiconductordistributed Bragg reflector, in which a low refractive indexsemiconductor layer and a high refractive index semiconductor layer arelaminated alternately, is used widely in view of the easiness of formingtogether with the active layer with excellent control and in view of thepossibility of flowing the careers that are used for driving the laserdiode.

For the material of the semiconductor distributed Bragg reflector, thosematerials that cause no optical absorption of the light produced in theactive layer (generally, the materials of wider bandgap than the activelayer) and those materials that achieve lattice matching to thesubstrate are used so as to avoid lattice relaxation. Here, thereflectance of the reflector has to be extremely high, up to 99% ormore, wherein the reflectance is increased by increasing the number ofthe layers. However, when the number of the layers is increased, itbecomes difficult to produce the surface-emission laser diode. Becauseof this, it is preferable that there is a large refractive indexdifference between the low refractive index layer and the highrefractive index layer.

AlAs and GaAs are the end-components of the AlGaAs system and haverespective lattice constants generally equal to that of GaAs used forthe substrate. Because of their compositions, it is possible to achievea large refractive index difference. Thus, the semiconductor multilayermirror of Al (Ga)As/GaAs, more broadly the AlxGa1-xAs/AlyGa1-yAs(0≦y<x≦1) structure is suitable for use as the reflector of asurface-emission laser diode.

However, sufficient emission efficiency was not obtained conventionallywhen the Al(Ga)As/GaAs semiconductor multilayer mirror was used as thereflector of a surface-emission laser diode. As verified with theexperiments mentioned before, the material containing Al is chemicallyvery reactive and easily forms crystal defects originating from Al.Thus, the Al source material or the Al source reactants remaining in thereaction chamber react with the water content or alcohol in thehydrazine source during the growth of the active layer containing theGaInNAs material, and the water or alcohol thus incorporated into thecrystal form the crystal defect that causes the non-opticalrecombination. Thereby, the efficiency of optical emission has beendegraded.

Because of this, there are proposals in Japanese Laid-open PatentApplication 08-340146 official gazette and Japanese Laid-Open 07-307525official gazette to form semiconductor distributed Bragg reflector fromGaInP and GaAs and that do not contain Al. However, the refractive indexdifference between GaInP and GaAs is about one half in comparison withthe refractive index difference between AlAs and GaAs, and there hasbeen a problem in that the number of layers in the reflector hasincreased very much and the production thereof becomes difficult.Further, the yield falls off and the device resistance increases. Inaddition, the time needed for the production is increased and the totalthickness of the surface-emission laser becomes thick. Further, theelectrical wiring becomes difficult.

On the contrary, the present invention supplies the nitrogen sourcematerial of a nitrogen compound to the reaction chamber after making acontact with the metallic Al or the alloy containing the metallic Al.Thereby, the amount of incorporation of oxygen into the active layer isreduced even when the AlxGa1-xAs/AlyGa1-yAs (0≦y<x≦1) semiconductormultilayer film is used for the reflector of the surface-emission laserdiode and fabrication of a surface-emission laser diode becomes possibleby using a semiconductor multilayer reflector providing a highreflectance with small number of the layers, while using a high qualityactive layer in which the number of the defects is reduced. Accordingly,it is possible to obtain a surface-emission laser diode having a simpleconstruction and produced with high yield, low cost and characterized bylow device resistance, low threshold current, high emission efficacy,high reliability and excellent temperature characteristic.

In the present invention, it is also possible to construct an opticaltelecommunication system that uses a laser diode (surface-emission laserdiode) as an optical source, by forming the group III–V compoundsemiconductor film containing nitrogen (N) by the GaInNAs material andusing the GaInNAs material for the active layer.

FIG. 36 shows an example of a parallel transmission type opticaltelecommunication system that used the surface-emission laser diodearray of the present invention mentioned above.

FIG. 36 is referred to. In the optical transmission system of thedrawing, the signals from plural surface-emission laser diodes 622driven by electrical signals 621A from an electrical signal processingunit 621 are transmitted in parallel corresponding photodetector array624 via plural optical fibers 623. The electrical signals that formed asa result of optical detection in the photodetector array 624 areprocessed in an electrical signal processing unit 625.

FIG. 37 is shows an example of the wavelength multiplexing opticaltelecommunication system that uses the surface-emission laser diodearray of the present invention mentioned above.

FIG. 37 is referred to. In the optical transmission system of thedrawing, the optical signals from the plural surface-emission laserdiodes 622 driven by the electrical signals 621A from the electricalsignal processing unit 621 are injected into a single optical fiber 623Tfrom plural optical fibers 623 and also an optical wave synthesizer wave623A, and the wavelength multiplexing optical signal thus produced istransmitted through the single optical fiber 623.

The wavelength multiplexed optical signal thus transmitted through theoptical fiber 623T are divided into plural optical signals by a divider623B and are supplied to corresponding photodetection device array 624via optical fibers 623. The electric signals formed by thephotodetection in the photodetection device array 624 are processed inthe electric signal processing unit 625.

<Embodiment 10>

In Embodiment 10, the epitaxial growth film of GaN material was grown ona GaN substrate was selectively grown by using the semiconductor filmgrowth apparatus (MOCVD apparatus) of the present invention, andproduced a laser diode. The MOCVD apparatus that was used was the onehaving the construction shown in FIG. 30.

In other words, the MOCVD apparatus that was used in the embodiment 10had a susceptor having a heater in a reaction chamber 61 evacuated tolow pressure by a vacuum pump, and there is provided a source materialsupply line that supplies TMG, TMA, TMI into the reaction chamber 61with the H₂ gas as a carrier gas. Furthermore, there are provided sourcegas lines for supplying SiH₄ (silane) and Zn(CH₃)₂ (DMZn) into thereaction chamber 61 as the doping gas of n-type and p-type,respectively. Furthermore, there is provided a line supplying the NH₃gas, and a nitrogen source refinement unit 65 filled with the particlesof an AlGaIn alloy in a cylinder is provided midway of this line.

Here, the particles of the AlGaIn alloy were formed in the followingmanner.

In a nitrogen gas atmosphere, the AlGaIn alloy is molten in a BNcrucible and is dropped into a refrigerated fluorinated oil (FONPRINYL-VAC14/6 of AUSIMONT S.p.A) to form the particles of AlGaIn alloy of1–5 mm diameter. The alloy particles thus formed are filled up in thecylinder in the nitrogen gas atmosphere. In such a construction, thenitrogen source gas is transported to the reaction chamber 61 with thecarrier gas of an H₂ gas after passed through the refinement unit 65.

In Embodiment 10, a laser diode shown in FIG. 38 was produced by usingthe MOCVD apparatus of FIG. 30.

Thus, an amorphous GaN buffer layer 702 was grown at the substratetemperature 550° C. on a c-oriented sapphire single crystal substrate701 with a thickness 200 Å, and a foundation GaN layer 703 was grownsubsequently to the thickness of 2 μm at the substrate temperature 1050°C.

Next, the sample was taken out into the atmosphere from the MOCVD growthchamber and an SiO₂ film 704 was grown to the thickness of 0.1 μm by aCVD process. By processing the SiO₂ film 704 by photo lithography andwet etching process, a mask pattern was formed to have a stripe windowhaving a width of 4 μm with the period of 11 μm.

Further, the foregoing sample is returned to the MOCVD growth chamberonce again and an n-type GaN film 705 is grown selectively on the maskpattern at the substrate temperature of 1050° C. Thereby, the GaN filmgrows laterally from the buffer GaN layer 702 on the mask pattern and adefect-free high-quality single crystal film 705 having a large area isobtained. Such a growth film is called selective growth film or ELOGsubstrate (epitaxially laterally overgrown GaN substrate). Subsequently,an n-type GaN contact layer 706, an n-type AlGaN cladding layer 707, ann-type GaN guide layer 708, a triple MQW active layer 709 ofIn_(0.02)Ga_(0.98)N/In_(0.15)Ga_(0.85)N, a p-type GaN guide layer 710, ap-type AlGaN cladding layer 711, and a p-type GaN contact layer 712,were grown consecutively and epitaxially.

Next, a ridge stripe structure shown in FIG. 38 is formed by applying alaser processing process, and produced a broad stripe laser diode byforming a p-side electrode 713 on the p-type GaN contact layer 712 andan n-side electrode 714 on the n-type GaN contact layer 706.

The threshold current of this laser diode was 50 mA for continuousoscillation at the room temperature. For the purpose of comparativeexample, a broad stripe laser of the same construction was producedwithout using the nitrogen source refinement unit 65 in the MOCVDapparatus that was used in the experiment before. It turned out that thethreshold current of continuous laser oscillation, was 80 mA at the roomtemperature.

From this, it will be noted that the high-quality GaN film containinglittle impurity was obtained in the present invention as a result ofsupplying a NH₃ gas from which water content or alcohol is removed tothe reaction chamber 61, by passing the nitrogen source material (NH₃)through the nitrogen source material refinement unit 65. With this, itbecame possible to produce a ridge-stripe laser capable of carrying outcontinuous oscillation at room temperature with a reduced thresholdelectric current.

<Embodiment 11>

In Embodiment 11, a laser diode was produced by using the MOCVDapparatus shown in FIG. 31.

Thus, the MOCVD apparatus used in the present embodiment has a susceptorequipped with a heating means in the reaction chamber 61, wherein thereaction chamber is evacuated by a vacuum pump to low pressure. Further,there are provided lines for supplying TMG, TMA, TMI, AsH₃, PH₃, SeH₂,Zn(CH₃)₂ to the reaction chamber 61 with the H₂ gas as a career gas.Furthermore, there is provided a bubbler 92 holding thereindimethylhydrazine, and the refinement unit 65 is provided between thebubbler 92 and the reaction chamber 61.

The refinement of the source material is achieved in the refinement unit65 as follows.

A liquid of GaInAl (100:10:1.8 in weight) is held in the refinement unit65 and the vapor of hydrazine is bubbled with the career gas of H₂.After the gas is refined, it is transported to the reaction chamber 61.

In Embodiment 11, the laser diode shown in FIG. 20 was formed by usingthe MOCVD apparatus of FIG. 31.

Thus, a broad stripe laser was produced on an n-type GaAs substrate 720by forming a lower cladding layer 721 of n-type AlGaAs, a GaAsintermediate layer 722, an active layer 723 of a GaInNAs/GaAs doublequantum well structure, a GaAs intermediate layer 724, a p-type AlGaAsupper cladding layer 725 consecutively, and further forming a p-sideelectrode (stripe electrode) 726 on the p-type cladding layer 725 and ann-side electrode 727 on the rear side of the substrate 720.

In the broad stripe laser diode thus obtained, the Al concentration inthe active layer 723 was 1×10¹⁸ cm⁻³ or less and the oxygen (O)concentration in the active layer 723 was 2×10¹⁷ cm⁻³ or less. Further,the threshold current for continuous laser oscillation at the roomtemperature was 25 mA.

As a comparative example, a broad stripe laser of the same constructionwas formed without using the refinement unit 65 in the same MOCVDapparatus. It turned out that the active layer of the laser diode thusformed contained Al with 2×10¹⁹ cm⁻³ or more and oxygen with 1×10¹⁸ cm⁻³or more. Further, it was confirmed that the threshold current was veryhigh and takes a value of 250 mA or more in the case of continuousoscillation at the room temperature.

As can be seen from this, it became possible to obtain a high-qualityGaInNAs film containing little impurity by passing the nitrogen sourcematerial (hydrazine) through the nitrogen source refinement unit 65 andsupplying the refined hydrazine gas from which water or alcohol isremoved to the reaction chamber 61 in the present invention. Thereby, itbecame possible to fabricate a broad stripe laser having a low thresholdcurrent and capable of causing a continuous oscillation at the roomtemperature.

<Embodiment 12>

In Embodiment 12, a surface-emission laser diode was produced by usingthe MOCVD apparatus shown in FIG. 40. In FIG. 40, those parts explainedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

The MOCVD apparatus of FIG. 40 has a susceptor equipped with a heater inthe reaction chamber 61 evacuated to low pressure by the vacuum pump 66,and there are provided source supply lines TMG, TMA, TMI, AsH₃, PH₃,SeH₂, Zn(CH₃)₂ to the reaction chamber 61 together with high purity H₂gas as the carrier gas.

Further, the MOCVD apparatus has a bubbler 92 that holdsdimethylhydrazine, and there is provided a refinement unit 65 betweenthe bubbler 92 and the reaction chamber 61. This refinement unit 65 isconnected to the pump 94 via a first vacuum valve 93. Further, there isprovided a resistance heating boat 95 in the refinement unit 65 and ametallic Al film 96 is deposited on the inner surface of the refinementunit container by an evaporation deposition process.

In the MOCVD apparatus of such a construction, the refinement unit 65 isshut off from the supply line by closing a first line valve 97A and alsoa second line valve 97B, before introducing hydrazine into the reactionchamber 61. Further, the evaporation deposition of Al is conducted onthe inner surface of the refinement unit 65 by opening the gate valve 98and evacuating by the vacuum pump 94.

Next, the gate valve 98 is closed and the first line valve 97A and thesecond line valve 97B are opened. Thereby, the vapor of DMHy iscontacted with the Al-deposited surface 96 while using an H₂ gas as thecarrier gas. The vapor of DMHy is transported to the reaction chamber 61after being contacted with the Al-deposited surface 96.

In Embodiment 3, a surface-emission laser diode shown in FIGS. 41A and41B was produced by using the apparatus of FIG. 40. It should be notedthat FIG. 41B is a partially enlarged view of FIG. 41A.

The manufacturing process of the surface-emission laser diode of FIGS.41A and 41B is as follows.

A lower mirror layer 1902 is formed on a (100)-oriented n-type GaAssubstrate 1901 by repeating the n-type AlAl/n-type GaAs structure for 28times, and a first GaAs spacer layer 1903 and a multiple quantum wellactive layer 1904, consisting of three layers of GaInNAs active layer1904 a and two layers of GaAs barrier layer 1904 b, is formed on thelower mirror layer 1902. Further, a second GaAs spacer layer 1905 and anAlAs selective oxidation layer 1906 are formed consecutively, and anupper mirror layer 1907, in which a p-type AlGaAS/p-type GaAs structureis repeated for 20 times, is formed thereon. Further, a p-type GaAscontact layer 1908 is formed.

Next, an ECR etching process is applied to the layered structure thusobtained by using a Cl₂ gas up to the depth of the AlAs selectiveoxidation layer 1906, such that there remains a semiconductor pillar ofpost shape in the region of 30 μm×30 μm in correspondence the laseroscillation part. The semiconductor pillar may be formed to the heightof 6.0 μm, for example.

Next, a water vapor is applied to the side wall of the semiconductorpillar to form a current confinement layer 1906 b of insulating AlxOy,starting from the sidewall of the selective oxidation AlAs film 1906,while remaining the current path with the cross-sectional area of about25 μm² at the central part. Next, a non-photosensitive polyimide 1910 isformed by a spin coating process and is cured at 350° C., so that theheight thereof from the base part becomes 4.0 μm.

Next, a resist is applied, and polyimide film 1910 is removed from theregion of 28 μm×28 μm of the semiconductor pillar surface by alithography process and an RIE etching process that uses and O₂ gas.

Further, a p-side electrode 1911 and a wiring pattern are formed on theregion of the semiconductor pillar surface excluding the optical-beamexit part from which the polyimide film is removed and also on thepolyimide surface by way of vacuum evaporation deposition and lift-offprocess of an electrode film. Further, an n-side electrode 1912 isformed on the rear side of the substrate 1901.

In the surface-emission laser diode thus produced, the Al concentrationin the active layer 1904 was 1×10¹⁸ cm⁻³ or less and the oxygenconcentration was 2×10¹⁸ cm⁻³ or less. Further, it was confirmed thatthe threshold is 0.7 mA in the case of continuous laser oscillation in aroom temperature environment.

As a comparative example, a surface-emission laser diode of the sameconstruction was produced without using the refinement unit 65 in thesame MOCVD apparatus. In this laser diode, it was confirmed that theactive layer 904 contains Al with a concentration of 3×10¹⁹ cm⁻³ or moreand oxygen with 2×10¹⁸ cm⁻³ or more. Further, the threshold current wasconfirmed to be a remarkably large value of 4 mA or more in thecondition of continuous laser oscillation under a room temperatureenvironment.

As can be seen from this, the present mode of the invention enablesfabrication of a surface-emission laser diode having a lower thresholdcurrent and capable of continuous laser oscillation at room temperatureas a result of formation of high quality GaInNAs system film containinglittle impurities, by supplying the hydrazine source from which watercontent and alcohol are removed to the reaction chamber as a result ofcausing to flow the nitrogen source material (hydrazine) through thenitrogen source refinement unit.

[Fourteenth Mode of Invention]

FIGS. 42A and 42B are the diagrams showing an example of the productionapparatus of the semiconductor light-emitting device according to afourteenth mode of the present invention. It should be noted that FIGS.42A and 42B show the cross-sectional view of the reaction chamber(growth chamber) of the MOCVD apparatus.

FIGS. 42A and 42B are referred to. A reaction chamber (growth chamber)1301 has a construction of lateral type reactor and has a source gasinlet port 1304 and an exhaust port 1306. Further, a substrate 1302 onwhich the growth of the semiconductor light-emitting device is made anda susceptor 1303 holding the substrate 1302 are provided inside thereaction chamber (growth chamber) 1301.

The production apparatus of the semiconductor light-emitting device ofthe fourteenth mode is a production apparatus of the semiconductorlight-emitting device in which there is provided a semiconductor layercontaining Al between the substrate and the active layer containingnitrogen, and the active layer containing nitrogen and the semiconductorlayer containing Al are grown respectively by using a nitrogen compoundsource material and an organic-metal Al source. In the productionapparatus, there is provided the means 1305, between the inner wall ofthe reaction chamber (growth chamber) 1301 and the gas flow containingthe organic-metal Al source, for preventing Al species such as theorganic-metal Al source, Al reactant, Al compound or Al, from remainingon the inner wall of the reaction chamber (growth chamber) 1301 when thesemiconductor layer containing Al is grown. In the example of FIGS. 42Aand 42B, the means is an insert tube 1305.

In the production apparatus of semiconductor light-emitting devices ofsuch a construction, the source gas introduced from the source gas inlet1304 causes a growth of a semiconductor layer on the surface of thesubstrate 1302 by a chemical reaction, wherein the substrate 1302 isheld on a susceptor 1303 maintained at high temperature by resistanceheating, and the like,

Meanwhile, in this fourteenth mode, an insert tube 1305 is disposedbetween the inner wall of the reaction chamber 1301 and the source gasflow in the vicinity where the substrate 1302 is held, and this inserttube 1305 is provided movable back and forth within the reaction chamber1301 while causing little fluctuation in the atmosphere or pressure.FIG. 42A shows the state in which the insert tube 1305 is located in thevicinity of the substrate 1302, while FIG. 42B shows the state in whichthe insert tube 1305 is moved to the rear part of the reaction chamber1301 from the state of FIG. 2A.

When a semiconductor layer containing Al is grown with a source gascontaining an Al source material, there occurs no deposition (noresidue) of Al source on the inner wall of the reaction chamber(chamber) 1301, provided that the insert tube 1305 is located in thevicinity of substrate 1302 as shown in FIG. 42A. In this case, the Alsource material, and the like, is adsorbed on the inner side of theinsert tube 1305. Thus, when the insert tube 1305 is pulled out to therear part of the reaction chamber 1301 as it shown in FIG. 42B at thetime of growing the active layer containing nitrogen, no Al sourcematerial, and the like, remains on the inner wall of the reactionchamber 1301 in the vicinity of substrate 1302, and as a result, itbecomes possible to prevent the material containing Al from making acontact with the nitrogen compound source material or the impuritycontained in such a nitrogen compound source material and beingincorporated into the substrate 1302. Thereby, a semiconductorlight-emitting device of low threshold is grown.

According to the production apparatus and process of fabricating thesemiconductor light-emitting device of the fourteenth mode, it becomespossible to produce a semiconductor light-emitting device of the samestructure as shown in FIG. 5, in which a semiconductor layer 202containing Al is provided between the substrate 201 and the active layer204 containing nitrogen.

As mentioned before, it is effective to suppress the material containingAl from remaining in the reaction chamber 1301 for improving theefficacy of optical emission when fabricating a semiconductorlight-emitting device that has a semiconductor layer containing Albetween the substrate and the active layer containing nitrogen,particularly in view of the fact that existence of residualAl-containing material in the reaction chamber becomes a cause ofdegradation of efficiency of optical emission. In this fourteenth mode,the problem of adsorption of the material containing Al on the innerwall of the reaction chamber 1301 is prevented by providing the inserttube 1305 in the vicinity of the substrate 1302 in the process ofgrowing the semiconductor layer containing Al. As a result, it becomespossible to produce a high-efficiency semiconductor light-emittingdevice characterized by high emission efficiency.

[Fifteenth Mode Of Invention]

FIG. 43 is a diagram showing an example of a production apparatus of asemiconductor light-emitting device according to a fifteenth mode of thepresent invention. It should be noted that FIG. 43 is a diagram showingthe cross-sectional view of the reaction chamber (growth chamber) of theMOCVD apparatus.

In the example of FIG. 43, the reaction chamber (growth chamber) 1311 isformed of a lateral type reactor and has a source gas inlet port 1314, aside flow gas inlet port 1315 and an exhaust port 1316. A substrate1312, on which growth of a semiconductor light-emitting device is made,and a susceptor 1313 holding the substrate 1312 thereon are providedinside the reaction chamber (growth chamber) 1311.

The production apparatus of the semiconductor light-emitting device ofthe fifteenth mode is an apparatus for producing a semiconductorlight-emitting device having a semiconductor layer containing Al betweenthe substrate and the active layer containing nitrogen. In theproduction apparatus, an active layer containing nitrogen and asemiconductor layer containing Al are grown by using a nitrogen compoundsource material and an organic-metal Al source, respectively. Theproduction apparatus has a structure to cause a flow of a side-flow gasalong the inner wall of the reaction chamber (growth chamber) 1311 whengrowing the semiconductor layer containing Al and/or the active layercontaining nitrogen.

In the production apparatus of the semiconductor light-emitting deviceof such a construction, the source gas introduced from the source gasinlet port 1314 causes a growth of a semiconductor layer on the surfaceof a substrate 1312 held on a susceptor 1313, which in turn ismaintained at high temperature by resistance heating, and the like, by achemical reaction

On the other hand, the side-flow gas not containing a source gas isintroduced from the side-flow gas inlet port 1315, and the side-flow gasis caused to flow along the inner wall of the reaction chamber 1311.With this side-flow gas, contact of the source gas or materials formedas a result of the chemical reaction contact is prevented from making acontact with the inner wall of the reaction chamber 1311. In the case ofpyrolitic CVD process, for example, it is generally practiced to coolthe reaction chamber (reactor) by cooling water, and the like. In such acase, because of the low temperature of the inner wall of the reactionchamber, adsorption of the source gas or the material formed by thechemical reaction thereon is enhanced. On the other hand, by causing toflow the side-flow gas along the inner wall of the reaction chamber1311, the problem of the source gas or the substance produced as aresult of the chemical reaction making a contact with the inner wall ofreaction chamber 1311 is eliminated. Further, the side-flow gas alsoprevents the material adsorbed on the inner wall of the reaction chamber1311 from migrating to the substrate 1312.

According to the production apparatus and the process of fabricating thesemiconductor light-emitting device of the fifteenth mode, it ispossible to produce the semiconductor light-emitting device having astructure shown in FIG. 5 in which the semiconductor layer 202containing Al is provided between the substrate 201 and the active layer204 containing nitrogen.

As noted before, it is effective to eliminate the residual materialcontaining Al from the reaction chamber for improving the efficacy ofoptical emission in view of the fact that the Al-containing materialremaining in the reaction chamber 1311 becomes a factor of causingdegradation of the efficacy of optical emission at the time ofproduction of the semiconductor light-emitting device in which thesemiconductor layer containing Al is provided between substrate and theactive layer.

In this fifteenth mode, there is provided a step of introducing aside-flow gas not containing a source gas into reaction chamber 1311simultaneously with the source gas in the process of growing asemiconductor layer containing Al such that the source gas flows alongthe inner wall of the reaction chamber 1311. With this, the adsorptionof the material containing Al on the inner wall of the reaction chamber1311 is prevented, and as a result, it becomes possible to produce ahigh semiconductor light-emitting device of high emission efficiency.

In this fifteenth mode, it becomes possible to prevent the materialcontaining Al and remaining on the inner wall of the reaction chamber1311 being incorporated into the active layer in the form coupled withthe nitrogen source compound or water content and the like contained inthe nitrogen compound source material, by causing to flow the side-flowgas not containing a source gas along the inner wall of the reactionchamber 1311 simultaneously to the source gas in the step of growing theactive layer containing nitrogen. Thus, it is possible to prevent thematerial containing Al and adsorbed on the inner wall of the reactionchamber 1311 from making a contact with the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial and being incorporated into the active layer by causing to flowthe side-flow gas along the inner wall of the reaction chamber 1311 atthe time of growing the active layer containing nitrogen, even in thecase the material containing Al is adsorbed on the inner wall of thereaction chamber 1311. With this, it is possible to produce asemiconductor light-emitting device of low threshold.

Although it is possible to obtain the same effect even in the case apurging process for removing the material containing Al is provided,such an approach can eliminate the time needed for the purging process,and the production time of the semiconductor light-emitting device isreduced.

FIG. 44 is a diagram showing a modification of the production apparatusof the semiconductor light-emitting device of FIG. 43. It should benoted that FIG. 44 is a schematic diagram showing the cross-sectionalview of the reaction chamber of the MOCVD apparatus as viewed from alateral direction. In FIG. 44, those parts corresponding to FIG. 43 aredesignated by the same reference numerals.

In the example of FIG. 44, the reaction chamber 1311 is configured inthe form of a vertical reactor and there is provided a substrate 1312,on which the semiconductor light-emitting device is grown, in thereaction chamber 1311 together with a susceptor 1313 that holds thesubstrate 1312 thereon.

In the production apparatus of a semiconductor light-emitting device ofsuch a construction, the source gas introduced from a source gas inlet1314 causes a growth of a semiconductor layer by a chemical reaction onthe surface of substrate 1312 held on susceptor 1313 at high temperatureby resistance heating, and the like.

Thus, the operation of the example of FIG. 44 is basically the same asthe example of FIG. 43, and a similar effect as in the case of theexample of FIG. 43 can be obtained in the example of FIG. 44. It shouldbe noted that the MOCVD apparatus using the vertical reactor as in thecase of FIG. 44 has an advantage of achieving homogeneity of filmthickness and is used in the mass production of surface-emission laserdiode in which there is a demanded on the uniformity of the filmthickness.

[Sixteenth Mode of Invention]

FIG. 45 is a diagram showing an example of the construction of theproduction apparatus of semiconductor light-emitting device according toa sixteenth mode of the present invention. It should be noted that FIG.45 is a schematic view showing the lateral cross sectional view of areaction chamber (growth chamber) 1331 of the MOCVD apparatus as viewedfrom a top direction thereof.

In the example of FIG. 45, the reaction chamber 1331 is configured inthe form of a lateral type reactor and has a source gas inlet port 1334,a side-flow gas inlet port 1335 and an evacuation port 1336. Further, asubstrate 1332, on which the growth of the semiconductor light-emittingdevice is conducted, and a susceptor 1333 holding the substrate 1332thereon are provided within the reaction chamber (growth chamber) 1331.

It should be noted that the semiconductor light-emitting deviceproduction apparatus of the sixteenth mode is a production apparatus ofa semiconductor light-emitting device that includes a semiconductorlayer containing Al between a substrate and an active layer containingnitrogen and causes a growth of the active layer containing nitrogen andthe semiconductor layer containing Al by using a nitrogen compoundsource and an organic-metal Al source. The production apparatus has astructure that causes to flow the side-flow gas along the sidewall ofthe susceptor 1333 that carries thereon the substrate 1332 when growingthe semiconductor layer containing Al or when growing the active layercontaining nitrogen. More specifically, the side-flow gas inlet 1335 isprovided with a gas outlet such that the side-flow gas thus effusedtherefrom flows along the inner wall of the reaction chamber 1331 and apart of the side-flow gas flows along the sidewall of the susceptor 1333in the constructional example of FIG. 45.

In the production apparatus of semiconductor light-emitting device ofsuch a construction, the source gas was introduced from the source gasinlet 1334 causes a growth of a semiconductor layer by a chemicalreaction taking place on the surface of the substrate 1332 held on thesusceptor 1333, which in turn is held at a high temperature byresistance heating. Further, a side-flow gas not containing the sourcegas is introduced from the side-flow gas inlet port 1335. There, theside-flow gas flows along the inner wall of the reaction chamber 1331and a part of the side flow gas flows along the sidewall of thesusceptor 1333.

By causing to flow the side-flow gas along the sidewall of the susceptor1333, the problem of the source gas or the material formed as a resultof the chemical reaction causing an adsorption on the sidewall of thesusceptor 1333 is suppressed, and migration of the material containingAl and adsorbed to on the sidewall of the susceptor 1333 to thesubstrate 1312 is prevented. As the susceptor 1333 is located close tothe substrate 1332, the risk that the nitrogen compound source materialor the impurity such as water, and the like, contained in the nitrogencompound source is incorporated into the active layer in the formcoupled with the residual material containing Al is increased at thetime of growing the active layer in the case a material containing Al isadsorbed on the sidewall of the susceptor 1333. In this sixteenth mode,it is possible to reduce this risk and grow a semiconductorlight-emitting device of high efficiency of optical emission by causingto flow the side flow-gas along the sidewall of the susceptor 1333.

As noted above, the fifteenth or sixteenth mode of the present inventioncauses to flow the side-flow gas between the inner wall of the reactionchamber (growth chamber) and the gas flow containing the organic-metalAl source, when growing a semiconductor layer containing Al, so as toprevent residual of Al species such as the organic-metal Al source, anAl reactant, an Al compound, or Al. Thus, adsorption of the materialcontaining Al on the inner wall of the reaction chamber is prevented bycausing to flow the side-flow gas, when growing the semiconductor layercontaining Al, such that residual of Al species such as the Al source,Al reactant, Al compound or Al on the inner wall of the reaction chamberis eliminated, and incorporation of Al into the active layer containingnitrogen is suppressed. As a result, incorporation of oxygen, whichbecomes the cause of the non-optical recombination, into the activelayer that contains nitrogen is suppressed, and it become possible toproduce a high-efficiency semiconductor light-emitting device.

In the fifteenth and sixteenth mode of the present invention, it shouldbe noted that the side-flow gas is caused to flow between the inner wallof the reaction chamber (growth chamber) and the gas flow containing thenitrogen compound source material when growing the active layer thatcontains nitrogen. As such, it becomes possible to prevent the residualmaterial containing Al in the form couples with the is nitrogen compoundsource or with the impurity such as water, and the like, contained inthe nitrogen compound source material into the active layer, by causingto flow the side-flow gas, when growing the active layer containingnitrogen, so as to prevent migration of the residual Al species such asorganic-metal Al source, Al reactant, Al compound, or Al remaining onthe inner wall of the reaction chamber to the substrate. As a result,incorporation of oxygen, which becomes the cause of non-opticalrecombination, is suppressed, and becomes possible to produce asemiconductor light-emitting device having a high efficiency of opticalemission.

In the fifteenth and sixteenth mode, the side-flow gas is caused to flowso that that the residual of the Al species such as the Al sourcematerial, Al reactant, Al compound, or Al remaining on the inner wall ofthe reaction chamber (growth chamber) is prevented when growing thesemiconductor layer containing Al. Further, the side-flow gas is causedto flow so as to prevent the migration of the Al source material, Alreactant, Al compound, or Al remaining on the inner wall of the reactionchamber (growth chamber) to the substrate when growing the active layercontaining nitrogen. Like this, the side-flow gas is caused to flow sothat the residual of the Al source material, Al reactant, Al compound,or Al on the reaction chamber inner wall is prevented when growing thesemiconductor layer containing Al. Further, the side-flow gas is causedto flow so as to prevent the migration of the Al source material, Alreactant, Al compound, or Al that remaining on the reaction chamberinner wall to the substrate when growing the active layer containingnitrogen. With this, the material containing Al is prevented fromcausing adsorption inside the reaction chamber, and at the same time,the problem of incorporation of the residual material containing Al intothe active layer in the form coupled with the nitrogen compound sourcematerial or the impurity such as water contained in the nitrogencompound source material, is eliminated. As a result, incorporation ofoxygen, which becomes the cause of non-optical recombination, issuppressed, and as a result, a semiconductor light-emitting devicehaving a high efficiency of optical emission is produced.

Like this, it becomes possible to produce a semiconductor light-emittingdevice of high efficiency of optical emission, by the production methodand apparatus of semiconductor light-emitting device mentioned above.

FIG. 46 is a diagram showing an example of the surface-emission laserdiode produced by the production method of semiconductor light-emittingdevice and by the production apparatus of semiconductor light-emittingdevice according to the present invention.

FIG. 46 is referred to. The surface-emission laser diode is formed on ann-type GaAs substrate 1351 and includes a layered structure in which ann-type semiconductor multilayer reflector 1352, a GaAs lower part spacerlayer 1353, a GaInNAs/GaAs multiple quantum well active layer 1354, aGaAs upper part spacer layer 1355, an AlAs layer 1356, and a p-typesemiconductor multilayer reflector 1357 are laminated consecutively.

Here, the n-type semiconductor multilayer reflector 1352 is formed of adistributed Bragg reflector, which in turn is formed of alternatelamination of an n-type GaAs high refractive index layer and an n-typeAl 0.8Ga0.2As low refractive index layer. Similarly, the p-typesemiconductor multilayer reflector 1357 is also formed of a distributedBragg reflector that in which a p-type GaAs high refractive index layerand a p-type Al0.8Ga0.2As low refractive index layer are laminatedalternately.

Further, the GaInNAs/GaAs multiple quantum well active layer 1354 has abandgap wavelength of the 1.3 .mu.m band. Further, there is formed anoptical resonator from the GaAs lower part spacer layer 1353 to the GaAsupper part spacer layer 1355.

It should be noted that the stacked structure is etched up to the n-typesemiconductor multilayer reflector 1352, and there is formed acylindrical mesa structure having a diameter of 30 μmφ. Further, acurrent confinement structure is formed by selectively oxidizing theside wall of the AlAs layer 56 exposed as a result of the mesa etchingto form an insulation region having a composition represented as AlOx.In this case, the electric current is concentrated to an oxide openingregion of about 5 μmφ formed in the AlOx insulation region, and theelectric current is injected into the active layer 1354 in this state.

Further, a ring-shaped p-side electrode 1358 is formed on the surface ofthe p-type semiconductor multilayer reflector 1357, and an n-sideelectrode 1359 is formed on the rear side of the n-type GaAs substrate1351.

In the surface-emission laser diode of such a construction, the thatradiated in the GaInNAs/GaAs multiple quantum well active layer 1354 isamplified as it is reflected by the semiconductor multilayer reflectors1352 and 1357 at the top and bottom, and there is formed a laser beam ofthe 1.3 μm band such that the laser beam is emitted in the directionperpendicular to the substrate 1351.

In the surface-emission laser diode of such a construction, it should benoted that the type that uses the AlGaAs/GaAs stacking structure is mostsuitable for the semiconductor multilayer reflector 1352 formed on theGaAs substrate 1351 in view of easiness of producing a highly efficientreflector and easiness of providing excellent electric property. Asexplained previously, however, the quality of the active layer 1354 hasbeen deteriorated when attempt is made to grow the reflector 1352 withthe AlGaAs/GaAs stacking structure in the case of growing asurface-emission laser diode that uses an active layer containingnitrogen by an MOCVD process, and it has been not possible to obtain alow threshold current device. By using the production apparatus and theproduction process of the present invention, it becomes possible toproduce a low-threshold surface-emission laser diode that uses an activelayer 1354 of GaInNAs, and the like, even in the case of using asemiconductor multilayer reflector 1352 of having the AlGaAs/GaAsstacking structure.

[Seventeenth Mode of Invention]

FIG. 47 shows an example of the semiconductor light-emitting deviceaccording to a seventeenth mode of the present invention.

FIG. 47 is referred to. The semiconductor light-emitting device of thismode has a layered structure formed on a substrate 201 in which a firstsemiconductor layer 211 containing Al as a constituent element, a secondsemiconductor layer 212 containing Al as a constituent element, a lowerintermediate layer 203, an active layer 204 containing nitrogen, anupper intermediate layer 203 and a third semiconductor layer 213 arestacked consecutively.

The semiconductor light-emitting device of FIG. 47 is formed by anepitaxial growth process that uses an organic-metal Al source and anorganic nitrogen source material. Thereby, there is provided a process,after the growth of the first semiconductor layer 211 containing Al as aconstituting element but before the start of growth of the secondsemiconductor layer 212 contains Al as a constituent element, forremoving the residual Al species such as the Al source material, Alreactant, Al compound or Al remaining in the location of the growthchamber which may make a contact with the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial.

By providing the above process, it becomes possible to remove theresidual Al species such as the Al source material, Al reactant, Alcompound or Al remaining in the location of the growth chamber where thenitrogen compound source material or the impurity contained in thenitrogen compound source material may make a contact, by causing agrowth of the first semiconductor layer 211 that contains Al as aconstituent element.

FIG. 48 is a diagram showing the room temperature photoluminescencespectrum of the GaInNAs/GaAs double quantum well structure. In FIG. 48,the reference B is for the case in which the GaInNAs/GaAs double quantumwell structure is formed on a GaInP layer while the reference A is forthe case in which the same double quantum well structure is formed on anAlGaAs layer having a thickness of 1.5 μm. Further, the reference C isfor the case that in which the double quantum well structure is formedon the AlGaAs layer of the thickness of 0.2 μm.

As shown in FIG. 48, it becomes possible to obtain a photoluminescentintensity comparable to the case in which the active layer formed on aGaInP layer, also in the case the active layer is formed on an AlGaAslayer, provided that the thickness of the AlGaAs layer underneath theactive layer containing nitrogen, is set thinner than the thickness of1.5 μm, which thickness is used generally for the cladding layer of thesemiconductor light-emitting device, to the thickness of 0.2 μm, forexample.

This is because the concentration of the residual Al species such as theAl source material, Al reactant, Al compound or Al remaining in thelocation of the growth chamber, in which the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial may make a contact, is reduced by reducing the thickness of thelayer of the semiconductor layer containing Al and is located below theactive layer containing nitrogen.

Thereupon, in the semiconductor light-emitting device of the seventeenthmode of the present invention, there is provided a process of removingthe residual Al species such as the Al source material, Al reactant, Alcompound or Al from the location of the growth chamber which may make acontact with the nitrogen compound source material or the impuritycontained in the nitrogen compound source material, after the growth ofthe first semiconductor layer 211 that contains Al as a constituentelement. Next, the second semiconductor layer 212 containing Al isprovided with a thickness smaller than the thickness of thesemiconductor layer 211 that contains Al, and the active layer 204containing nitrogen is formed thereafter.

Thus, the residual Al species such as the Al source material, Alreactant, Al compound or Al remaining as a result of the growth of thefirst semiconductor layer 501 containing Al are removed once. Further,by reducing the thickness of the second semiconductor layer 502containing Al to the thickness of 0.2 μm, for example, the concentrationof the residual Al species such as the Al source material, Al reactant,Al compound or Al is reduced, and thus, the concentration of theimpurity that forms the non-optical recombination levels in the activelayer 204 containing nitrogen is reduced. With this, it is possible toachieve a continuous room-temperature oscillation of the semiconductorlight-emitting device of FIG. 5, in which an active layer containingnitrogen is laminated on a semiconductor layer containing Al.

FIG. 56 is a diagram showing the depth profile of nitrogen concentrationand oxygen concentration of the semiconductor light-emitting device inwhich the process of removal of the Al species such as the Al sourcematerial, Al reactant, Al compound or Al from the location of the growthchamber where nitrogen compound source material or the impuritycontained in the nitrogen compound source material is conducted duringthe process of growing the lower intermediate layer 203. It should benoted that the measurement was conducted by the SIMS process.

In the experiment of FIG. 56, it should be noted that the substrate istransported from the reaction chamber into the sample exchange chamberas the process of removing Al, and the reaction chamber is subjected tovacuum evacuation process, followed by a carrier gas purging process,wherein the carrier gas purging is continued for one hour.

FIG. 56 is referred to. It can be seen that the concentration of oxygenthat forms the non-optical recombination level is below the backgroundlevel in the active layer 204 that contains nitrogen. This is obviouslythe result of providing the process of removing Al in the midway ofgrowing the lower intermediate layer 203.

In the case, a growth interruption is made during the growth of thelower intermediate layer 203 for providing the Al removal process, apeak of oxygen is being detected at the interface, indicating that thereexists segregation of oxygen at the interface. While not shown in FIG.56, the peaks of C and Si are detected other than oxygen.

Similarly to the case of the semiconductor light-emitting device of FIG.47 explained previously, there can be caused a similar segregation ofimpurity such as oxygen, C, Si, and the like, at the interface betweenthe first semiconductor layer 211 containing Al the second semiconductorlayer 212 containing Al wherein there is provided the process of removalthe residual Al such as the Al source material, Al reactant, Alcompound, or Al from the part of the growth chamber that may make acontact with the w nitrogen compound source material or the impuritycontained in the nitrogen compound source material.

The impurity such as oxygen, C, Si, and the like, that has segregated tothe interface forms a non-optical recombination level. In thesemiconductor light-emitting device of FIG. 47, on the other hand, itshould be noted that the second semiconductor layer 212 containing Al isprovided between the growth interruption interface formed as a result ofremoval of the residual Al and the active layer 204 containing Al.Because the bandgap energy of the second semiconductor layer 212containing Al is larger than that of the intermediate layer 203, thecareers that have caused overflow from the active layer 204 containingnitrogen to the intermediate layer 203 are blocked by the semiconductorlayer 212 of large bandgap. Thus, the proportion of loss of the overflowcarriers at the non-optical recombination levels in the growthinterruption surface by causing a recombination is reduced as comparedwith the case of providing a growth interruption interface in theintermediate layer 203. As a result, the leakage current is suppressedand it becomes possible to form a highly efficient semiconductorlight-emitting device.

[Eighteenth Mode of Invention]

In eighteenth mode of the present invention, the semiconductorlight-emitting device has a feature similar to that described in theseventeenth mode, except that the concentration of the impurity formingthe non-optical recombination level in the active layer containingnitrogen is the same as the concentration in the intermediate layer orless.

Here, it should be noted that the intermediate layer is formed of amaterial not containing Al and N as a constituent element, and thus,direct contact between the semiconductor layer containing Al and theactive layer containing nitrogen is avoided. With this, exposure of Al,which shows a strong chemical bond or affinity with nitrogen, iseliminated at the time the nitrogen source material is supplied to thegrowth chamber for growing the active layer containing nitrogen, and theproblem of abnormal segregation on the surface is suppressed.

In the case an active layer, such as a GaAs or GaInAs active layer notcontaining nitrogen, is formed on a semiconductor layer containing Al byan MOCVD process, no problem or deterioration of optical emissioncharacteristics is reported for the active layer thus grown.Accordingly, it becomes possible to obtain a high-quality active layerfree from deterioration by reducing the concentration level of theimpurity that forms a non-optical recombination level in the activelayer containing nitrogen, to the order of the impurity concentrationlevel of the intermediate layer not containing nitrogen. Thus, anoptical emission characteristic comparable to the case of forming anactive layer containing nitrogen on a semiconductor layer not containingAl, is obtained even in the case the active layer containing nitrogen isformed on a semiconductor layer containing Al as a constituent element.

[Nineteenth Mode of Invention]

In a semiconductor light-emitting device according to a nineteenth modeof the present invention, the semiconductor light-emitting device has aconstruction explained previously with reference to seventeenth mode,except that the oxygen concentration in the active layer containingnitrogen is set to a concentration that enables a continuous roomtemperature oscillation.

Table 4 described before shows the result of evaluation of thresholdcurrent density in which a broad stripe laser is experimentally producedby using AlGaAs for the cladding layer (layer containing Al) and using aGaInNAs double quantum well structure (a layer containing nitrogen) asthe active layer.

From Table 4, it can be seen that oxygen is incorporated into the activelayer with a concentration of 1×10¹⁸ cm⁻³ or more in the structure inwhich the active layer containing nitrogen is grown continuously to thesemiconductor layer containing Al as a constituent element, and it canbe seen also that a remarkably high value or 10 kA/cm² or more isobtained for the threshold current density. However, it becomes possibleto oscillate the broad stripe laser with a threshold current density of2–3 kA/cm², by reducing the oxygen concentration in the active layer to1×10¹⁸ cm⁻³ or less. When the quality of the active layer is such thatthe threshold current density of the broad stripe laser is severalkA/cm² or less, it is possible for the laser diode that uses such anactive layer to cause a continuation laser oscillation at a roomtemperature. Accordingly, it is possible to produce a laser diodecausing a continuous oscillation at a room temperature, by suppressingthe oxygen concentration in the active layer containing nitrogen to1×10¹⁸ cm⁻³ or less.

In the nineteenth mode of the present invention, the oxygenconcentration in the active layer containing nitrogen is reduced to thelevel of 1×10¹⁸ cm⁻³ or less, by conducting the process of removing theresidual Al species such as the Al source material, Al reactant, Alcompound or Al from the location of the growth chamber where thenitrogen compound source material or the impurity contained in thenitrogen compound source material may make a contact after the growth ofthe first semiconductor layer containing Al, and further by providing asecond semiconductor layer containing Al with a reduced thickness. Inthis way, it became possible to form a semiconductor light-emittingdevice that can oscillate continuously at a room temperature, byreducing the non-optical recombination in the active layer such that theefficiency of optical emission is improved.

[Twentieth Mode of Invention]

From the measurement of the depth profile of the oxygen concentrationshown in FIG. 6 previously, it will be noted that the oxygenconcentration in the intermediate layer 203 in the construction of FIG.5 is 2×10¹⁷–7×10¹⁶ cm⁻³. Accordingly, it is possible to provide anactive layer of high quality by reducing the oxygen concentration in theactive layer containing nitrogen to at least 2×10¹⁷ cm⁻³.

As shown in Table 4 explained previously, a threshold current density of0.8 kA/cm², which is comparable to the value of the threshold currentdensity for the case of using a GaInP cladding layer, is obtained evenin the case an AlGaAs cladding layer is used in the broad stripe laser.

Accordingly, in the twentieth mode of the present invention, thesemiconductor light-emitting device of the eighteenth mode is formedsuch that the oxygen concentration in the active layer containingnitrogen is 2×10¹⁷ cm⁻³ or less. By setting the oxygen concentration ofthe active layer containing nitrogen to be equal to or smaller than theoxygen concentration of the intermediate layer, for example, an opticalemission characteristic comparable with the case of forming the activelayer containing nitrogen on a semiconductor layer free from Al isobtained also in the case the active layer containing nitrogen is formedon the semiconductor layer containing Al as a constituent element.

[Twenty-First Mode of Invention]

Table 4 explained before shows the result of evaluation of the thresholdcurrent density for the case of producing experimentally a broad stripelaser while using AlGaAs for the cladding layer (layer containing Al)and the GaInNAs double quantum well structure (layer containingnitrogen) as the active layer.

In the structure in which the active layer containing nitrogen is formedcontinuously to the semiconductor layer that contains Al as aconstituent element like this, it should be noted that the active layercontains Al with a concentration of 2×10¹⁹ cm⁻³ or more and a remarkablyhigh threshold current density of 10 kA/cm² or more is obtained.However, when the oxygen concentration in the active layer is reduced to1×10¹⁸ cm⁻³ or less by reducing the Al concentration in the active layerto 1×10¹⁹ cm⁻³ or less, it becomes possible to oscillate the broadstripe laser with a threshold current density of 2–3 kA/cm². In the casethe threshold current density of a broad stripe laser is several kA/cm²,it is possible to cause a continuous oscillation in a laser diode at theroom temperature by using the active layers of the same quality.Accordingly, it is possible to produce a laser diode capable ofoscillating at the room temperature by suppressing the Al concentrationin the active layer containing nitrogen to the level of 1×10¹⁹ cm⁻³ orless.

Thus, according to the twenty-first mode of the present invention, asemiconductor light-emitting device containing a substrate, a firstsemiconductor layer containing Al and laminated on the substrate, and anactive layer containing nitrogen and formed on the first semiconductorlayer containing Al, is formed by providing a step of removing theresidual Al species, between the first semiconductor layer containing Aland the active layer containing nitrogen, such as the residual Al sourcematerial, Al reactant, Al compound or Al, from the part of the growthchamber that may make a contact with the nitrogen compound source or theimpurity contained in the nitrogen compound source. Thereafter, a secondsemiconductor layer containing Al and having a reduced thickness ascompared with the first semiconductor layer containing Al is provided.By setting the Al concentration of the active layer containing nitrogento be 1×10¹⁹ cm⁻³ or less, the efficiency of optical emission in theactive layer is improved. Like this, it becomes possible to form asemiconductor light-emitting device that causes continuous oscillationat the room temperature in this mode of the present invention.

[Twenty-Second Mode of Invention]

In a twenty-second mode of the present invention, the Al concentrationof the active layer containing nitrogen is set, in the semiconductorlight-emitting device of the twenty-first mode, to be equal to orsmaller than the Al concentration of the intermediate layer.

From FIG. 8 noted previously, it can be seen that the Al concentrationin the intermediate layer 203 grown without supplying the nitrogencompound source material and the organic-metal Al source to the reactionchamber is 2×10¹⁸ cm⁻³ or less. In the case the Al concentrationincorporated into the active layer is 2×10¹⁸ cm⁻³ or less, it ispossible to reduce the oxygen impurity concentration level in the activelayer to be 2×10¹⁷ cm⁻³ or less.

As shown in Table 4 noted previously, a threshold current density of 0.8kA/cm², which is equivalent to the case of using a GaInP cladding layer,is obtained even in the case of using an AlGaAs cladding layer in thebroad stripe laser, by reducing the Al concentration in the active layerto 1×10¹⁸ cm⁻³ or less.

Accordingly, an optical emission characteristic equivalent to the casein which the active layer is formed on a he semiconductor layer notcontaining Al is obtained also in the case of setting the Alconcentration of the active layer containing nitrogen to be 2×10¹⁹ cm⁻³or less, preferably 1×10¹⁸ cm⁻³ or less, even in the case that theactive layer containing nitrogen is formed on the semiconductor layerthat contains Al as a constituent element. In this case, the Alconcentration of the active layer is set equal to or smaller than the Alconcentration of the intermediate layer.

[Twenty-Third Mode of Invention]

In a twenty-third mode of the present invention, the Al content of thesecond semiconductor layer 212 containing Al is set smaller than the Alcontent of the first semiconductor layer 211 also containing Al in thesemiconductor light-emitting device of the seventeenth throughtwenty-second mode.

More specifically, the thickness of the second semiconductor layer 212containing Al is set smaller than the thickness of the firstsemiconductor layer 211 containing Al, and in addition, the Al contentof the second semiconductor layer 212 containing Al is set smaller thanthe Al content of the first semiconductor layer 211 containing Al. Withthis, the concentration of the residual Al species such as the Al sourcematerial, Al reactant, Al compound, or Al, remaining in the part of thegrowth chamber where the nitrogen compound source material or theimpurity contained in the nitrogen compound source material may make acontact is reduced further. With this, the efficiency of opticalemission of the active layer is improved and a semiconductorlight-emitting device characterized by a low threshold current isrealized.

[Twenty-Fourth Mode of Invention]

FIG. 49 is a diagram showing the construction of a semiconductorlight-emitting device according to a twenty-fourth mode of the presentinvention. Those parts corresponding to the parts explained previouslyare designated by the same reference numerals and explanation thereofwill be omitted.

The semiconductor light-emitting device of FIG. 49 is constructed on thesubstrate 201 and includes a consecutive stacking of the firstsemiconductor layer 211 containing Al as a constituent element, theintermediate layer 221, the second semiconductor layer 212 containing Alas a constituent element, the lower part intermediate layer 203containing Al as a constituent element, the active layer 204 containingnitrogen, the upper part intermediate layer 203 and the thirdsemiconductor layer 213.

It should be noted that the semiconductor light-emitting device of FIG.49 is formed by an epitaxial growth that uses a metal-organic Al sourceand an organic nitrogen source material. In the construction of FIG. 49,the intermediate layer 221 is provided between the first semiconductorlayer 211 containing Al and the second semiconductor layer 212, andthere is provided a process of removing the residual Al species such asthe Al source material, Al reactant, Al compound, or Al from the part ofthe growth chamber where the nitrogen compound source material or theimpurity contained in the nitrogen compound source material may make acontact, in the midway of the intermediate layer.

By providing the above process, it becomes possible to remove theresidual Al species such as the Al source material, Al reactant, Alcompound, or Al remaining in the part of the growth chamber where thenitrogen compound source material or the impurity contained in thenitrogen compound source material may make a contact, as a result ofgrowth of the first semiconductor layer 211 that contains Al.

For example, the intermediate layer 221 is composed of a semiconductormaterial such as GaAs that does not contain Al. By interrupting thegrowth of the intermediate layer 221 and by providing the Al removalprocess, the segregation of impurity such as O during the interruptionof the growth is suppressed as compared with the case in which the Alremoval process is conducted immediately after the growth of the firstsemiconductor layer 211, and it becomes possible to suppress formationof the non-optical recombination levels at the growth interface.Accordingly, the non-optical recombination levels are reduced from thegrowth interface and the efficiency of optical emission of the activelayer is improved.

[Twenty-Fifth Mode of Invention]

FIG. 50 is a diagram showing the construction of a surface-emissionsemiconductor light-emitting device according to a twenty-fifth mode ofthe present invention. Those parts corresponding to the parts explainedpreviously are designated with the same reference numerals andexplanation thereof will be omitted.

The semiconductor light-emitting device of FIG. 50 has a constructionsimilar to the semiconductor light-emitting device explained previouslywith reference to FIG. 11 and includes, on the semiconductor singlecrystal substrate 201, a consecutive stacking of the first lower partsemiconductor multilayer reflector 801, the second lower partsemiconductor multilayer reflector 802, the lower part spacer layer 803,the intermediate layer 203, the active layer 204 containing nitrogen,the intermediate layer 203 and the upper part multilayer reflector 804.Furthermore, the upper part spacer layer 805 is formed between the upperpart intermediate layer 203 and the upper part multilayer reflector 804.The optical beam is emitted in a vertical direction (upward direction)to the substrate 201.

For example, the semiconductor single crystal substrate 201 is formed ofa GaAs substrate 1 and the first lower part multilayer reflector 801 andthe second lower part multilayer reflector 802 are formed of adistributed Bragg reflector in which a semiconductor layer of lowrefractive index and a semiconductor layer of a high refractive indexare stacked alternately with an optical wavelength thickness of 1/4 theoscillation wavelength. As the combination of the high refractive indexlayer and the low refractive index layer, it is possible to use any ofGaAs/AlxGa1-xAs (0<x≦1), AlxGa1-xAs/AlyGa1-yAs (0<x<y≦1),GaInP/(AlxGa1-x) InP (0<x≦1), and the like.

The region from the lower part spacer layer 803 up to the upper partspacer layer 805, sandwiched by the reflector 802 and the reflector 805,constitutes an optical cavity and has an optical wavelength thickness ofan integer multiple of one-half the oscillation wavelength.

The intermediate layer 203 is formed with a material not containing Aland N, such as GaAs, GaInP, GaInAsP, and the like.

For example, the active layer 204 containing nitrogen is formed ofGaNAs, GaInNAs, GaNAsSb, GaInNAsSb, and the like. It should be notedthat such a nitride group V mixed crystal semiconductor material has abandgap wavelength of the 1.2–1.6 μm band and can cause an epitaxialgrowth on a GaAs substrate. Also, the active layer 204 is not limited toa single layer but may be configured in the form of a multiple quantumwell structure that uses a semiconductor layer containing nitrogen as awell layer.

Similarly to the lower part semiconductor multilayer reflector 801, theupper part multilayer reflector 804 forms a distributed Bragg reflector.For the material, it is possible to form with a semiconductor crystallike the lower part reflectors 801 and 802. Further, it is also possibleto form the same with a dielectric material of SiO2/TiO2, and the like.

By using a semiconductor layer containing Al as a constituent element asthe low refractive index layer of the lower part semiconductormultilayer reflectors 801 and 802, it becomes possible to increase therefractive-index difference with respect to the high refractive indexlayer. With this, a high reflectance of 99% or more can be obtained witha reduced number the layers. When the number of the layers is decreased,the electric resistance or thermal resistance the semiconductormultilayer reflector is reduced, and the temperature characteristics areimproved.

In the case an edge-emission laser, the cladding layer may also beformed with a material not containing Al such as GaInP, InP, GaInAsP,and the like. In the case of a surface-emission laser, on the otherhand, it is necessary to use a semiconductor layer containing Al such asthe AlGaAs material system, for the low refractive index layer in thelower part semiconductor multilayer reflectors 801 and 802 so as toguarantee the operational temperature of 70° C. or more.

In the surface-emission laser in which it is necessary to form theactive layer 204 containing nitrogen on the lower part semiconductormultilayer reflector 801 containing Al, the degradation of theefficiency of optical emission in the active layer 204 containingnitrogen becomes a serious problem. Especially, the lower part reflectorhas to be formed with a large thickness of 5 μm or more in view of theneed of stacking 30 periods or more for obtaining high reflectance.Therefore, there inevitably occurs an increase of concentration of theresidual Al species such as the Al source material, Al reactant, Alcompound, or Al that remains in the part of the growth chamber in whichthe nitrogen compound source material or the impurity contained in thenitrogen compound source material may make a contact.

According to the present invention, there is conducted a process forremoving the residual Al species such as the Al source material, Alreactant, Al compound, or Al from the part of the growth chamber wherethe nitrogen compound source material or the impurity contained in thenitrogen compound source material may make a contact, after the growthof the first lower part-semiconductor multilayer reflector 801containing Al. With this, the Al source material, Al reactant, or Alcompound, or Al remaining in the growth chamber is removed once by thegrowth of the first lower part semiconductor multilayer reflector 801.

After that, the second lower part semiconductor multilayer reflector 802containing Al is grown. In the present mode of the invention, theconcentration of Al remaining in the growth chamber is reduced byreducing the thickness thereof. Thereby, the efficiency of opticalemission in the active layer 204 containing nitrogen is improved.

Because the layer thickness of the second semiconductor multilayerreflector 802 containing Al is preferably reduced for reducing theconcentration of the residual Al species, the multilayer reflector 802may be constructed so as to include one period or less.

Also, the process for removing the residual Al species such as the Alsource material, Al reactant, Al compound, or Al from the part of thegrowth chamber where the nitrogen compound source material or theimpurity contained in the nitrogen compound source material may make acontact, may be provided by interrupting the grow of the high refractiveindex layer in the semiconductor multilayer reflector. Because the highrefractive index layer is formed of a material of very small Al content,like GaAs or Al_(0.1)Ga_(0.9)As, it is possible to suppress thesegregation of the impurities such as O at the growth interruptionsurface during the interruption of the growth. Thereby, formation ofnon-optical recombination levels on the growth interface is suppressed.

The thickness of the high refractive index layer, the process of removalof Al is conducted in the midway of growth thereof, is not limited tothe 1/4 optical wavelength thickness of the oscillation wavelength butmay be set to be n times the 1/4 optical wavelength thickness of theoscillation wavelength (n=1, 3, 5 . . . ) such that the phase alignmentcondition of light is met.

[Twenty-Sixth Mode of Invention]

A twenty-sixth mode of the present invention provides the process ofproducing of a semiconductor light-emitting device shown in any ofseventeenth through twenty-fifth mode.

In the twenty-sixth mode, there is provided a step of removing theresidual Al source, Al reactant, or Al compound or Al from the part ofthe growth chamber where the nitrogen source compound or the impuritycontained in the nitrogen source compound may make a contact, after thegrowth of the first semiconductor layer containing Al but before thestart of growth of the second semiconductor layer, or during the growthof an intermediate layer provided between the first semiconductor layercontaining Al and the second semiconductor layer.

More specifically, there is provided a process of removing the residualAl species such as the Al source material, Al reactant, Al compound, orAl from the part of the growth chamber which the nitrogen compoundsource material or the impurity contained in the nitrogen compoundsource material may make a contact, by way of a purging process thatuses a carrier gas.

In the present mode of the invention, the purging process is carried outafter the growth of the first semiconductor layer containing Al isterminated and the supply of the Al source material is suspended and iscontinued until the supply of the Al source material to the growthchamber is started for starting the growth of the second semiconductorlayer containing Al.

When a semiconductor layer containing Al as a constituent element isgrown, there remains residual Al species such as the Al source material,Al reactant, Al compound, or Al in the growth chamber. However, it ispossible to gradually decrease the concentration of Al remaining in thegrowth chamber, by purging the interior of the growth chamber by acarrier gas. In this way, it is possible to reduce the concentration ofAl and oxygen incorporated into the active layer even in the case theactive layer containing nitrogen is formed on the semiconductor layerthat contains Al as a constituent element. Thereby, the efficiency ofoptical emission of the active layer is improved.

Furthermore, it is as well possible to provide the removal process ofresidual Al more than once during the growth process of thesemiconductor layer containing Al at the lower part of the active layercontaining nitrogen. By removing the residual Al species formed in thereaction chamber as a result of growth of the semiconductor layercontaining Al, before the residual Al concentration becomes too high, itis possible to reduce the time needed for the removal process such asthe carrier gas purging process.

<Embodiment 13>

FIG. 51 is a diagram showing the laser diode according to Embodiment 13of the present invention. In FIG. 51, those parts corresponding to theparts explained before are designated by the same reference numerals andthe description thereof will be omitted.

FIG. 51 is referred to. The laser diode of the present embodiment isconstructed of on the n-type GaAs substrate 901. It includes a layeredstructure of the n-type GaAs buffer layer 902 formed on the substrate901, the first n-type Al_(0.4)Ga_(0.6)As cladding layer 903 having athickness 1.5 μm, and the second n-type Al_(0.4)Ga_(0.6)As claddinglayer 904A having a thickness of 0.2 μm. Also it includes a consecutivestacking of the GaAs lower optical waveguide layer 905, the GaInNAs/GaAsmultiple quantum well active layer 906, the GaAs upper optical guidelayer 907, the p-type Al_(0.4)Ga_(0.6)As cladding layer 908, and thep-type GaAs contact layer 909 on the foregoing layered structure.

Further, a ridge-stripe structure having a width of 4 μm is formed inthe layered structure thus formed by a stripe etching process such thatthe part from the surface of the p-type GaAs contact layer 909 up to themidway of the p-type Al_(0.4)Ga_(0.6)As cladding layer 908 is removed.

Further. the p-side electrode 910 is formed on the p-type GaAs contactlayer 909, and the n-side electrode 911 is formed on the rear side ofthe n-type GaAs substrate 901.

The structure shown in FIG. 51 forms a ridge-stripe laser diode in whichthere occurs a confinement of electric current and light in theridge-stripe structure.

The crystal growth of the laser diode of FIG. 51 is conducted by using asingle MOCVD apparatus and by supplies TMG, TMA and TMI as the group IIIsource material and AsH₃ and DMHy as the V group source material.

The feature of Embodiment 13 exists in the point that there is provideda growth interruption process after the growth of the first n-typeAl_(0.4)Ga_(0.6)As cladding layer 903 but before the start of growth ofthe second n-type Al_(0.4)Ga_(0.6)As cladding layer 904A.

In the present embodiment, the growth chamber is purged by a carry gasduring the growth interruption process. By purging the growth chamberwith the carrier gas as such, the residual Al species such as the Alsource material, Al reactant, Al compound, or Al remaining in the growthchamber as a result of the growth of the n-type AlGaAs cladding layer903 are purged and the concentration thereof is reduced.

Furthermore, the concentration of Al and also oxygen incorporated intothe GaInNAs well layer is reduced sufficiently by forming the secondn-type Al_(0.4)Ga_(0.6)As cladding layer 904A grown after the growthinterruption and purging process with a small thickness of 0.2 μm.Thereby, degradation of the efficiency of optical emission issuppressed. With this, the GaInNAs system laser diode having an AlGaAscladding layer and characterized by low threshold current is realized.

<Embodiment 14>

FIG. 52 shows a laser diode according to a Fourteenth Embodiment of thepresent invention. Those parts corresponding to the parts describedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

FIG. 52 is referred to. Although the structure of the laser diode of thepresent embodiment resembles the structure of the laser diode of FIG.12, there exists a distinction in the point that an n-typeAl_(0.2)Ga_(0.8)As cladding layer 904B is provided with a thickness of0.2 μm in place of the second n-type Al_(0.4)Ga_(0.6)As cladding layer904A.

According to the present embodiment, it is possible to reduce theresidual Al species such as the Al source material, Al reactant, Alcompound or Al remaining in the part of the growth chamber which maymake a contact with the nitrogen source compound or the impuritycontained in the nitrogen source compound at the time of growing then-type Al_(0.2)Ga_(0.8)As cladding layer 904B, by reducing the thicknessof the n-type AlGaAs cladding layer 904B grown after the growthinterruption and purging process to 0.2 μm, and further by reducing theAl content therein than the Al content of the AlGaAs cladding layer 903.With this, the efficiency of optical emission of the active layer isimproved and it becomes possible to construct a GaInNAs system laserdiode of low threshold current.

<Embodiment 15>

FIG. 53 shows the construction of a laser diode according to Embodiment15 of the present invention. In the drawings, those parts correspondingto the parts described previously are designated by the same referencenumerals and the description thereof will be omitted.

Although the laser diode of FIG. 53 has a structure that resembles thelaser diode of FIG. 51, there exists a difference in the point that afirst intermediate layer 904 C of n-type GaAs and a second intermediatelayer 904D of n-type GaAs are laminated between the first n-type AlGaAscladding layer 903 and the second n-type AlGaAs cladding layer 904.

In Embodiment 15, there is provided a growth interruption process afterthe growth of the first n-type GaAs intermediate layer 904C but beforethe start of growth of second n-type GaAs intermediate layer 904D forpurging the growth chamber with a carrier gas. By purging the growthchamber with a carrier gas as such, the residual Al species such as theAl source material, Al reactant, Al compound, or Al remaining in thegrowth chamber as a result of growth of the n-type AlGaAs cladding layer903 are purged and the concentration thereof is reduced.

Further, because the intermediate layers 904C and 904D are formed ofGaAs, the problem of segregation of impurity such as oxygen on theuppermost surface during the growth interruption and purging process issuppressed, and formation of the non-optical recombination levels is onsuch a growth interface is suppressed. Thus, the non-opticalrecombination levels are reduced on the growth interface and theefficiency of optical emission of the active layer is improved further.

<Embodiment 16>

FIG. 54 shows the construction of a surface-emission laser diodeaccording to Embodiment 16 of the present invention. In the drawings,those parts corresponding to the parts described previously aredesignated by the same reference numerals and the description thereofwill be omitted.

FIG. 54 is referred to. The laser diode of the present invention has aconstruction similar to that of FIG. 13 explained previously andincludes the first n-type semiconductor multilayer reflector 1001, thesecond n-type semiconductor multilayer reflector 1002, the GaAs lowerpart spacer layer 1003, the GaInNAs/GaAs multiple quantum well activelayer 906, the GaAs upper part spacer layer 1004, the p-type AlAs layer1005 and the p-type semiconductor multilayer reflector 1006 formedconsecutively on an n-type GaAs substrate 901.

The N-type semiconductor multilayer reflector 1001 of the presentinvention is formed of a distributed Bragg reflector, which in turn isformed of an alternate repetition of an n-type GaAs high refractiveindex layer and an n-type Al 0.8Ga_(0.2)As low refractive index layer.Similarly, the p-type semiconductor multilayer reflector 1006 is formedof a distributed Bragg reflector in which a p-type GaAs high refractiveindex layer and a p-type Al_(0.8)Ga_(0.2)As low refractive index layerare laminated alternately.

The GaInNAs/GaAs multiple quantum well active layer 906 has a bandgapwavelength of the 1.3 μm band. Further, the part thereof from the firstGaAs lower part spacer layer 1002 up to the GaAs upper part spacer layer1004 constitutes a λ cavity.

The above stacked structure is etched in a cylinder form until then-type semiconductor multilayer reflector 1001 is reached, and as aresult, there is formed a mesa structure having a diameter of 30 μm (30μmφ).

Further, by oxidizing the p-type AlAs layer 1005 selectively from thesidewall surface exposed by the mesa etching process to form an AlOxinsulation region 1007, there is formed a current confinement structure.In such a current confinement structure, the electric current isconfined into an opening region formed in the oxide film with a size ofabout 5 μmφ by the AlOx insulation region 1007 and the electric currentthus confined is injected into the active layer 906.

Further, a ring-shaped p-side electrode 910 is formed on the surface ofthe p-type semiconductor multilayer reflector 1006, and an n-sideelectrode 911 is formed on the rear surface of the n-type GaAs substrate901.

In such a structure, the light radiated in the GaInNAs/GaAs multiplequantum well active layer 906 is amplified as it is reflected by the topand bottom semiconductor multilayer reflectors 1001, 1002 and 1006, anda laser beam of the 1.3 μm band is emitted in a direction perpendicularto the substrate (the direction of arrow of FIG. 54).

FIG. 55 shows the junction part between the first n-type semiconductormultilayer reflector 1001 and the second n-type semiconductor multilayerreflector 1002 of the surface-emission laser diode of FIG. 54 in detail.

As shown in FIG. 55, the first n-type semiconductor multilayer reflector1001 is formed of an alternate stacking of an n-type Al_(0.8)Ga_(0.2)Aslow refractive index layer 1001 a and an n-type GaAs high refractiveindex layer 1001 b. Further, any of the n-type Al_(0.8)Ga_(0.2)As lowrefractive index layer 1001 a and the n-type GaAs high refractive indexlayer 1001 b has an optical thickness of 1/4 the oscillation wavelengthof 1.3 μm. The uppermost layer of the first n-type semiconductormultilayer reflector 1001 is formed of an n-type GaAs high refractiveindex layer 1001 b having a 1/4 optical wavelength thickness.

The second n-type semiconductor multilayer reflector 1002 is formed bylaminating an n-type GaAs high refractive index layer 1002 a and ann-type Al_(0.4)Ga_(0.6)As low refractive index layer 1002 b, each withone layer. The n-type GaAs high refractive index layer 1002 a has anoptical thickness of 1/2 of the oscillation wavelength of 1.3 μm, whilethe n-type Al_(0.4)Ga_(0.6)As low refractive index layer 1202 b has anoptical thickness of 1/4 the oscillation wavelength of 1.3 μm.

Like this, there are formed n-type GaAs high refractive index layerswith the optical thickness of 3/4 the wavelength in total in thejunction part of the first n-type semiconductor multilayer reflector1001 and the second n-type semiconductor multilayer reflector 1002. Thissatisfies the condition of phase matching of light of the distributedBragg reflector.

In the present invention, the crystal growth of the layered structure isconducted in a single MOCVD apparatus by using AsH₃ and DMHy as thegroup V source material and TMG, TMA and TMI as the group III sourcematerial. Thereby, there is provided a growth interruption process afterthe growth of n-type GaAs high refractive index layer 1001 b forming theuppermost layer of the first n-type semiconductor multilayer reflector1001 but before the start of growth the n-type GaAs high refractiveindex layer 1002 a of the second n-type semiconductor multilayerreflector 1002.

By purging the growth chamber by flowing a carrier gas into the growthchamber in such a growth interruption process, the residual Al speciessuch as Al source material, Al reactant, Al compound, or Al remaining inthe growth chamber after the growth of the first n-type semiconductormultilayer reflector 1001 are purged, and the Al concentration isreduced.

It should be noted that the only semiconductor layer of the secondn-type semiconductor multilayer reflector 1002 containing Al and grownafter the growth interruption and purging process is the n-typeAl_(0.4)Ga_(0.6)As low refractive index layer 1002 b, which has athickness 0.1 μm. Thus, the thickness of the semiconductor layercontaining Al is small and may have a value of about 0.1 μm. Further,the Al content thereof is smaller than the Al content of the n-typeAl_(0.8)Ga_(0.2)As low refractive index layer 1001 a that constitutesthe first n-type semiconductor multilayer reflector 1001. With this, itbecomes possible to improve the efficiency of optical emission of theactive layer by reducing the Al concentration remaining in the growthchamber and hence reducing the concentration of Al and oxygenincorporated into the GaInNAs well layer. The growth interruption andpurging process is carried out between the n-type GaAs high refractiveindex layer 1002 b at the top of the first n-type semiconductormultilayer reflector 1001 and the n-type GaAs high refractive indexlayer 1001 a of the second n-type semiconductor multilayer reflector1002. In other words, it is conducted during the growth of the GaAsmaterial. It is known that GaAs is a stable material chemically inertand not easily form interface states as compared with the materialcontaining Al such as AlGaAs. Thus, by doing like this, formation of thenon-optical recombination levels on the growth interface is suppressed.

In the surface-emission laser diode of FIGS. 54 and 55, it should benoted that there is provided an n-type Al_(0.4)Ga_(0.6)As low refractiveindex layer 1002 b between the GaInNAs/GaAs multiple quantum well activelayer 906 containing nitrogen and the growth interruption interface. Thebandgap energy of n-type Al_(0.4)Ga_(0.6)As low refractive index layer1002 b is larger than that of the GaAs spacer layer 1002. Because ofthis, the carriers overflowed to the GaAs spacer layer 1002 from theGaInNAs/GaAs multiple quantum well active layer 906 are blocked by then-type AlGaAs low refractive index layer 1002 b having a large bandgap.Thus, the proportion that the carriers, overflowed from GaInNAs/GaAsmultiple quantum well active layer 906, are lost by causing arecombination at the non-optical recombination levels on the growthinterruption interface is reduced. Thereby, the leakage current isreduced and a highly-efficient 1.3 μm band surface-emission laser diodeis realized.

Although there is provided only one growth interruption process in thepresent embodiment, it is also possible to provide plural growthinterruption steps in the growth process of the n-type semiconductormultilayer reflector.

[Twenty-Seventh Mode of Invention]

FIG. 57 is a diagram showing the construction of a production apparatusof semiconductor light-emitting device according to a twenty-seventhmode of the present invention. It should be noted that FIG. 57 is adiagram showing the longitudinal cross-sectional view of the reactionchamber (growth chamber) of the MOCVD apparatus. In the drawings, thoseparts corresponding to the parts described previously are designated bythe same reference numerals and the description thereof will be omitted.In the construction of FIG. 57, it should be noted that the reactionchamber (growth chamber) 1301 is configured in the form of a lateralreactor similarly to the embodiment of FIGS. 42A and 42B and has asource gas inlet port 1304 and an exhaust port 1306. Further, asusceptor 1303 for supporting the substrate 1302 on which the growth ofthe semiconductor light-emitting device takes place, is provided in thereaction chamber (growth chamber) 1301. In the example of FIG. 57, thereis provided a heater 1307 heating the wall of the reaction chamber 1301,and the wall temperature of the reaction chamber 1301 is changed asdesired by the heater 1307.

In the production apparatus of the twenty-seventh mode, the source gasintroduced from the source gas inlet port 1304 causes to grow asemiconductor layer by a chemical reaction on the surface of thesubstrate 1302 held on the susceptor 1303, which in turn is held at ahigh temperature by the resistance heating, and the like.

Meanwhile, in the twenty-seventh mode, the reaction chamber 1301 isprovided with a heater 1307 for heating the wall thereof, and the walltemperature of the reaction chamber 1301 can be changed as desired bythe heater 1307. Thus, by raising the temperature of the wall of thereaction chamber 1301 by using the heater 1307, desorption of the sourcegas or a product formed as a result of the chemical reaction on theinner wall of the reaction chamber 1301 is promoted.

Thus, in the twenty-seventh mode of the present invention, there isprovided a method of producing a semiconductor light-emitting device inwhich a semiconductor layer containing Al is provided between thesubstrate and the active layer containing nitrogen, and the active layercontaining nitrogen and the semiconductor layer containing Al are grownby using a nitrogen compound source and an organic metal source of Alrespectively, wherein a purging process is conducted while holding thetemperature of the inner wall of the growth chamber 1301 at atemperature higher than the temperature used for growing the activelayer containing nitrogen, after the growth of the semiconductor layercontaining Al but before the growth of the active layer containing Al,such that the residual Al species such as the Al source material, Alreactant, Al compound or Al are purged from the inner wall of the growthchamber 1301.

As noted previously, removal of the material containing Al from thegrowth chamber is very effective for improving the efficiency of opticalemission of the semiconductor light-emitting device when producing asemiconductor light-emitting device in which a semiconductor layercontaining Al is provided between the substrate and the active layercontaining nitrogen, because of the fact that the residual of thematerial containing Al in the growth chamber is a major factor of thedegradation of efficiency of optical emission. In this twenty-seventhmode, the residual Al species such as the Al source gas or the reactionproduct containing Al adsorbed on the inner wall of the growth chamber1301 at the time of growing a semiconductor layer containing Al, ispurged with a gas such as hydrogen while heating the inner wall of thegrowth chamber 1301 for a predetermined time before growing the activelayer containing nitrogen. With this, the residual Al reaction productis eliminated from the inner wall of the growth chamber 1301, andincorporation of the residual material containing Al into the activelayer in the form coupled with the nitrogen compound source material orthe impurity such as water contained in the nitrogen compound sourcematerial is prevented.

In the twenty-seventh mode, a purge process is conducted between thegrowth of the semiconductor layer containing Al and the growth of theintermediate layer. Thereby, the temperature of the inner wall of thegrowth chamber 1301 is set higher than the temperature of the inner wallwhen growing the active layer. With this, the purge process is conductedin the state the desorption of the residual Al species occurs easierfrom the wall as compared with the case of growing the active layer, andit is possible to actually grow the active layer such that the residualAl species do not cause desorption from the wall. As a result,incorporation of the residual Al species into the substrate by making acontact with the nitrogen compound source material or the impuritycontained in the nitrogen compound source material is prevented, and itbecomes possible to grow a semiconductor light-emitting device of lowthreshold.

According to the above process, it becomes possible to conduct a purgingprocess effectively in a short time period as compared with the case ofconducting a purging process merely for removing the residual Alspecies.

[Twenty-Eighth Mode of Invention]

FIG. 58 is a diagram showing the construction of the productionapparatus of a semiconductor light-emitting device according to atwenty-eighth mode of the present invention. In FIG. 58, those partscorresponding to the parts described before are designated by the samereference numerals and the description thereof will be omitted.

In the example of FIG. 5, the reaction chamber (growth chamber) 1301 isconfigured in the form of a lateral type reactor and a source gas inletport 1304, a side-flow gas inlet port 1305 and an exhaust port 1306 areprovided. Also, a substrate 1302 on which growth of the semiconductorlight-emitting device takes place is provided in the chamber 1301together with a susceptor 1303 that holds the substrate 1302 thereon.

Further, a heater 1307 is provided for heating the wall of the reactionchamber 1301, and thus, it becomes possible to change the temperature ofthe wall of reaction chamber 1301 as desired by the heater 1307.

The feature of the production apparatus by this twenty-eighth mode ascompared with the production apparatus of the semiconductorlight-emitting device of the first mode is that it has a structure offlowing a side-flow gas along the inner wall of the reaction chamber(growth chamber) 1301 when growing the semiconductor layer containing Aland/or the active layer containing nitrogen.

In the production apparatus of semiconductor light-emitting device ofsuch a construction, the source gas introduced from the source gas inletport 1304 causes a growth of a semiconductor layer by a chemicalreaction on the surface of the substrate 1302 on the susceptor 1303,which is held at a high temperature by resistance heating, and the like.

On the other hand, a side-flow gas not containing the source gas isintroduced from the side-flow gas inlet 1305 so that the side-flow gasflows along the inner wall of the reaction chamber 1301. Further,desorption of the residual Al species such as the source gas or theproduct formed by a chemical reaction and adsorbed on the inner wall ofthe reaction chamber 1301 is promoted by raising the temperature of thewall of the reaction chamber 1301 by the heater 1307. Further,desorption of the residual Al species adsorbed on the inner wall ispromoted further in the process that carries out purging by heating thewall, by flowing the side-flow gas. As a result, incorporation of theresidual Al species into the substrate by causing a contact with thenitrogen compound source or the impurity contained in the nitrogencompound source is prevented, and a semiconductor light-emitting deviceof low threshold is grown.

Thus, the twenty-eighth mode of the present invention eliminates theresidual Al species such as the Al source, Al reactant, Al compound orAl by holding the temperature of the inner wall of the growth chamber ata temperature higher than the temperature of the inner wall of thegrowth chamber at the time of growing the active layer containingnitrogen and further by flowing the side-flow gas in the productionprocess of a semiconductor light-emitting device in which asemiconductor layer containing Al is provided between the substrate andthe active layer containing nitrogen and growing the active layercontaining nitrogen and the semiconductor layer containing Al by using anitrogen compound source and a metal organic Al source, after the growthof the semiconductor layer containing Al but before the growth of theactive layer containing nitrogen.

[Twenty-Ninth Mode of Invention]

FIG. 59 is a diagram showing the construction of a production apparatusof semiconductor light-emitting device according to a twenty-ninth modeof the present invention. In the drawings, those parts corresponding tothe parts described previously are designated by the same referencenumerals and the description thereof will be omitted.

In the construction of FIG. 59, it will be noted that the reactionchamber 1301 is a lateral type reactor, and the substrate 1302, on whichthe semiconductor light-emitting device is grown, and the susceptor 1303holding the substrate 1302, are provided within the reaction chamber1301.

In the construction of FIG. 59, the source gas introduced from thesource gas inlet 1304 causes a growth of a semiconductor layer by achemical reaction on the surface of the substrate 1302 on the susceptor1303, which is held at a high temperature by resistance heating, and thelike. By desorbing the Al species, such as the Al source gas or areactant containing Al and adsorbed on the susceptor 1303 at the time ofgrowing the semiconductor layer containing Al, by way of purging of theinterior of the reaction chamber 1301, which in turn is conducted by agas such as hydrogen and by heating the susceptor 1303 for apredetermined time before growing the active layer containing nitrogen,it becomes possible to prevent the nitrogen compound source or theimpurity such as water contained in the nitrogen compound source isincorporated into the active layer in the form coupled with the residualAl species. In the present mode, purging is conducted in the conditioneasier for the desorption from the susceptor 1303, by setting thetemperature of the susceptor 1303 higher than the temperature used forgrowing the active layer. Thereby, it becomes possible to eliminate thedesorption of the material containing Al from the susceptor 1303 whenthe active layer is actually grown. As a result, it becomes possible toeliminate incorporation of the residual Al species into the substrate bymaking a contact with the nitrogen compound source material or theimpurity contained in the nitrogen compound source material, and itbecomes possible to grow a semiconductor light-emitting device of lowthreshold.

Thus, the fifty-ninth mode of the present invention eliminates theresidual Al species such as the Al source, Al reactant, Al compound orAl from the susceptor in the production method of a semiconductorlight-emitting device in which a semiconductor layer is provided betweena substrate and an active layer containing nitrogen by growing theactive layer containing nitrogen and the semiconductor layer containingAl by using a nitrogen compound source material and a metal organic Alsource respectively, after the growth of the semiconductor layercontaining Al but before the growth of the active layer, by holding thetemperature of the susceptor holding the substrate at a temperaturehigher than the temperature used when actually growing the active layercontaining nitrogen.

[Thirtieth Mode of Invention]

FIG. 60 is a diagram showing the construction of the productionapparatus of a semiconductor light-emitting device according to athirtieth mode of the present invention. In the drawing, those partscorresponding to the parts described previously are designated by thesame reference numerals and the description thereof will be omitted.

In the example of FIG. 60, the growth chamber 1301 is a lateral typereactor and has a source gas inlet port 1304 and, a side-flow gas inletport 1305 and an evacuation port 1306. Also, a substrate 1302 on whichgrowth of the semiconductor light-emitting device takes place and asusceptor 3 holding the substrate are provided within the growth chamber1301. In such construction, the source gas introduced from the sourcegas inlet port 1304 causes a growth of a semiconductor layer on thesurface of the substrate 1302 held on the susceptor 1303, which in turnis held at a high temperature by resistance heating, and the like, by achemical reaction.

Further, a side-flow gas not containing the source gas is introducedfrom the side-flow gas inlet port 1305, and there is provided a gasoutlet 1305A such that the side-flow gas flows along the sidewall of thesusceptor 1303.

In this thirtieth embodiment, it is possible to eliminate incorporationof residual Al species into the active layer in the form coupled withthe nitrogen compound source or the impurity contained in the nitrogencompound source by purging the residual Al species such as the Al sourcegas or reactant containing Al and adsorbed on the susceptor 1303 at thetime of growth of the semiconductor layer containing Al, by way ofheating the susceptor 1303 for a predetermined time and flowing theside-flow gas such that the side-flow gas flows along the sidewall ofthe susceptor 1303, before the growth of the active layer containingnitrogen, such that desorption of the source gas or the material formedas a result of chemical reaction from the susceptor 1303 is facilitated.At this time, the temperature for heating the susceptor 1303 is sethigher than the temperature when growing the active layer. With this,the purging process is conducted in a state easier for desorbing fromthe susceptor 1303 as compared with the time of growing the activelayer. As a result, it is possible to prevent desorption of the materialcontaining Al from the susceptor 1303 at the time the active layer isactually grown. As a result, incorporation of the residual Al speciesinto the substrate by making a contact with the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial is eliminated, and it becomes possible to grow a semiconductorlight-emitting device of low threshold.

Thus, in the thirtieth mode of the present invention, there is provideda method of producing a semiconductor light-emitting device having asemiconductor layer containing Al between the active layer containingnitrogen and a substrate by growing the active layer containing nitrogenand the semiconductor layer containing Al by using a nitrogen sourcecompound and a metal organic Al source respectively, wherein theresidual Al species such as residual Al source, Al reactant, Al compoundor Al are removed from the susceptor after the growth of thesemiconductor layer containing Al but before the growth of the activelayer containing nitrogen, by setting the temperature of the susceptorholding the substrate to a temperature higher than the temperature ofthe susceptor used when growing the active layer containing nitrogen andconducting a purging process by flowing a side-flow gas along thesusceptor.

FIG. 61 is a diagram showing a modification of the production apparatusof the semiconductor light-emitting device of FIG. 60. It should benoted that FIG. 61 is a schematic longitudinal cross-sectional view ofthe reaction chamber of the MOCVD apparatus as viewed from a lateraldirection. In FIG. 61, those parts corresponding to the parts explainedpreviously are designated by the same reference numerals and explanationthereof will be omitted.

In the example of FIG. 61, it should be noted that the growth chamber1311 is a type of vertical tube and accommodates therein a substrate1312 on which growth of a semiconductor light-emitting device takesplace and a susceptor 1313 that holds the substrate 1312.

In the production apparatus of semiconductor light-emitting device ofsuch a construction, the source gas introduced from the source gas inletport 1314 causes a pyrolitic decomposition on the surface of thesubstrate 1312 held on the susceptor 1313, which in turn is held at ahigh temperature by resistance heating, and the like, and there iscaused a grow a semiconductor layer. Further, a heater is provided inthe reaction chamber 1311 for heating the wall, and it is possible tochange the temperature of the wall as desired. Like this, the example ofFIG. 61 is basically the same as the example of FIG. 60 in terms ofoperation thereof, and it is possible to obtain the effect similar tothe example of FIG. 60. Because the MOCVD apparatus that uses alongitudinal type reactor like the example of FIG. 61 easily providesuniformity of the film, it is widely used for the mass production of asurface-emission laser diode in which there is a demand of uniformity offilm thickness.

[Thirty-First Mode of Invention]

FIG. 62 is a diagram showing the construction of a production apparatusof the semiconductor light-emitting device according to a thirty-firstmode of the present invention. It should be noted that FIG. 62 is aschematic lateral cross sectional diagram of the reaction chamber of theMOCVD apparatus. In the drawings, those parts corresponding to the partsdescribed previously are designated by the same reference numerals andthe description thereof will be omitted.

In the construction of FIG. 62, the growth chamber 1301 is a sidelateral type reactor and has the source gas inlet port 1304, theside-flow gas inlet port 1305 and, the evacuation port 1306. Further,the substrate 1302 on which growth of the semiconductor light-emittingdevice and the susceptor 1303 holding the substrate 1302, are providedwithin the growth chamber 1301.

In such a construction, the source gas introduced from the source gasinlet port 1304 causes the growth of a semiconductor layer on thesubstrate surface on the susceptor 1303 held at high temperature byresistance heating, and the like, by a chemical reaction.

On the other hand, a side-flow gas not containing the source gas isintroduced from the inlet port 1305 and there is provided a nozzle 1305such that the side-flow gas flows along the inner wall of reactionchamber 1301 and the sidewall of the susceptor 1303.

In the example of FIG. 62, there is provided a heater 1307 for heatingthe wall in the reaction chamber 1301, and the temperature of the wallof the reaction chamber 1301 is changed as desired. Thus, by raising thetemperature of the wall by the heater 1307, the desorption of the sourcegas or the product formed as a result of the chemical reaction adsorbedon the inner wall of the reaction chamber 1301 is promoted.

Further, by flowing the side-flow gas in the purging process conductedby heating the wall, it becomes possible to promote the desorption ofthe source gas or the product formed by the chemical reaction andadsorbed on the inner wall, more effectively and more efficiently.Further, in the purging process that is conducted by heating thesusceptor 1303, the desorption of the source gas or material formed as aresult of the chemical reaction from the susceptor 1303 is facilitatedby flowing the side-flow gas along the sidewall of the susceptor 1303.With this, incorporation of the residual Al species into the activelayer containing nitrogen in the form coupled with the nitrogen compoundsource material or the impurity such as water content contained in thenitrogen compound source material is eliminated. By conducting thepurging by heating the wall of the reaction chamber 1301 andsimultaneously conducting the purging by heating the susceptor 1303, theeffect of purging is enhanced and it becomes possible to grow a hesemiconductor light-emitting device of low threshold.

Like this, the thirty-first mode of the present invention combines theprocesses of making the semiconductor light-emitting device of any ofthe twenty-seventh and twenty-eighth modes and the process of making asemiconductor light-emitting device of any of the twenty-ninth andthirties modes, and removes the residual Al species such as the Alsource material, Al reactant, Al compound, or Al from the growth chamberinner wall and also the susceptor.

Like this, it is possible to produce a semiconductor light-emittingdevice of high efficiency of optical emission explained with FIG. 46previously, by the production apparatus and process of a semiconductorlight-emitting device any modes explained above.

[Thirty-Second Mode of Invention]

FIG. 63 is a diagram showing the example of the production apparatus ofsemiconductor light-emitting device according to a thirty-second mode ofthe present invention. It should be noted that FIG. 63 shows thecross-sectional view of the growth chamber of the MOCVD apparatus. Inthe drawings, those parts corresponding to the parts describedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

In the example of FIG. 63, the growth chamber 1311 is a vertical typereactor, and a substrate 1312 on which a semiconductor light-emittingdevice is grown and a susceptor 1313 holding the substrate are supportedon a stage 1313A in the growth chamber 1311. The source gas introducedfrom the source gas inlet port 1314 is introduced over the substrate1312. The stage 1313A is provided with a heating mechanism by resistanceheating, and the source gas decomposes thermally at the substratesurface on the susceptor 1313 heated to a high temperature by theheating mechanism of this stage. As a result, there is caused a growthof the semiconductor layer on the substrate 1312.

The susceptor 1313 is provided detachably on the stage 1313A asrepresented in FIG. 63. As shown in FIG. 64, it is possible to removethe stage 1313A from the susceptor 1313 after drawing out the stage1313A from the reaction chamber 1311 to a second chamber 1311A providedfor the purpose of transportation, by transporting the susceptor 1321 toa substrate holding chamber 1321 together with the substrate 1312thereon. The growth chamber 1311, the transportation chamber 1311A andalso the substrate holding chamber 1311 can be divided by a gate valve,and the like, and the substrate holding chamber 1321 can be evacuatedindependently or purging with hydrogen, nitrogen, and the like. In thisway, it is possible to transport the susceptor 1313 and the substrate1312 to the reaction chamber 1311 in a hydrogen atmosphere.

In the substrate-holding chamber 1321, there are provided pluralsusceptors 1313. The substrate 1312 is lifted up by lift pins 1313P thatare moved upward from the small holes provided at the lower part of thesusceptor 1313 as shown in FIG. 65A, and the substrate 1312 can betransported as desired to another susceptor 1313 by a substratetransportation arm 1313Q. The transportation mechanism of the substrate1312 is not limited to the arm 1313Q but may be constructed by a vacuumchuck 1313R of FIG. 65B, and the like.

The susceptor in the substrate-holding chamber 1321 can be transportedto a desired susceptor in the reaction chamber. Thus, the substrate 1312can be transported to any desired susceptor 1313 in thesubstrate-holding chamber 1321 without being exposed to the air and itis possible to transport a desired susceptor 1313 to the reactionchamber 1311. Because of absence of exposure to the air at the time oftransportation, contamination of oxidation of the substrate caused byoxygen in the atmosphere is minimized.

In the thirty-second mode of the present invention, it is possible togrow the semiconductor light-emitting device of FIG. 5 by the two-stepprocess as follows.

First, a first semiconductor layer 202 containing Al is grown on thesubstrate 201. After the process that causes the growth of thesemiconductor layer 202 containing Al is finished, the susceptor 1313carrying a substrate 202 corresponding to the substrate 1312 istransported to the substrate holding chamber 1321 and is placed onanother susceptor 1313 already provided therein. The susceptor 1313provided in the substrate holding chamber 1321 is eliminated withadsorbed gases by conducting sufficient evacuation. Thus, it is possibleto prevent the contamination or oxidation of the substrate 1312 or thesusceptor 1313 at the time of transportation, by conducting a purgingprocess by a hydrogen gas.

The substrate 1312 now carried on the new susceptor 1313 is transportedto the reaction chamber 1311 together with the susceptor, and growth ofthe intermediate layer 203 and the active layer 204 is conductedsubsequently. Further, the intermediate layer 203 and the 2ndsemiconductor layer 205 containing Al are grown. Here, it should benoted that the change of the susceptor may be conducted at any timingafter the growth of the first semiconductor layer 202 containing Al butbefore the end of the growth of the lower intermediate layer 203. Forexample, the change of the susceptor 1313 may be conducted byinterrupting the growth of the lower intermediate layer 203 at a midwaythereof.

By using the process of changing the susceptor, it becomes possible touse a susceptor free from adsorption, not the susceptor on which thematerial containing Al is adsorbed, in the process of growing the activelayer. With this, incorporation of the residual Al species into theactive layer by causing a coupling with the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial is prevented, and it becomes possible to grow a semiconductorlight-emitting device of low threshold.

Thus, according to the production method of semiconductor light-emittingdevice and the production apparatus of the semiconductor light-emittingdevice of the present mode of the invention, in which a semiconductorlayer containing Al is provided between the substrate and the activelayer containing Al, the susceptor used for holding the substrate at thetime of growing the active layer containing nitrogen is changed from thesusceptor that is used for supporting the substrate at the time ofgrowing the semiconductor layer containing Al. With this, incorporationof the residual Al species being into the active layer by making acontact with the nitrogen compound source material or the impuritycontained in the nitrogen compound source material, and it becomespossible to grow a semiconductor light-emitting device of low threshold.

In the production apparatus of semiconductor light-emitting device ofthis mode, the susceptor used for growing the active layer containingnitrogen is made ready in a chamber different from the growth chamber inwhich the growth of the active layer containing nitrogen is conductedduring the process of growing a semiconductor layer containing Al, andthe susceptor thus prepared is changed with the susceptor used forgrowing the semiconductor layer containing Al after the growth of thesemiconductor layer containing Al is finished. Thereby, it is possibleto change the susceptor used for growing the semiconductor layercontaining Al with the susceptor used for growing the active layercontaining nitrogen, without exposing the substrate to the atmosphere.

FIG. 69 shows a modification of the production apparatus ofsemiconductor light-emitting device by the thirty-second mode of thepresent invention. It should be noted that FIG. 69 is a schematic viewshowing the longitudinal section of the reaction chamber of the MOCVDapparatus as viewed from a lateral direction. In the drawings, thoseparts explained previously are designated by the same reference numeralsand the explanation thereof will be omitted.

In the example of FIG. 69, the reaction chamber is a lateral typereactor. However, it should be noted that the fundamental constructionis common with the example of FIG. 63 and the same effect can beobtained.

Thus, in the apparatus of FIG. 69, the substrate 1302 on which growth ofthe semiconductor light-emitting device is conducted and the susceptor1303 holding the substrate 1302 are provided on a heated body 1303H inthe interior thereof. Here, the susceptor 1303 may be formed of carbonand a depression is provided on the susceptor 1303 for holding thesubstrate 1302. Further, the susceptor 1303 is provided on the heatedbody 1303H in a detachable manner. Further, the heated body 1303H ismade also with carbon, and it becomes possible to heat the susceptor1303 and the heated body 1303H by driving the induction coil 1307.

In such a construction, the source gas introduced from the source gasinlet port 1304 causes a pyrolitic decomposition on the surface of thesubstrate 1302 held on the heated susceptor 1303, and there is caused agrowth of a semiconductor layer. It should be noted that the susceptor1303 is removable from the heated body 1303H as shown in FIG. 70 and istransported to the substrate holding chamber 1321 after expelled to thetransport chamber 1301A together with the susceptor 1303 thereon. Thesubstrate holding chamber 1321 is configured so as to be purgedindependently by vacuum evacuation process or by using hydrogen,nitrogen, and the like. Thus, it is possible to transport the susceptor1303 and the substrate 1302 to the reaction chamber 1301 in a hydrogenatmosphere, and the like. A plurality of susceptors 1303 are providedready in the substrate holding chamber 1321, and the substrate 1302 onthe susceptor 1303 can move to any desired susceptor by vacuum chuck,and the like.

In such an apparatus, it is possible to growth of the semiconductorlight-emitting device of the construction of FIG. 5 with the sameprocess explained before.

Thus, it is possible to use a susceptor free from adsorption of thematerial containing Al at the time of growing the active layer, also inthe case of the lateral type reactor similarly to the case of thelongitudinal-type reactor by using the process of changing thesusceptor, without changing the susceptor. As a result, incorporation ofthe residual Al species into the active layer by making a contact withthe nitrogen compound source material or the impurity contained in thenitrogen compound source material, and as a result, it becomes possibleto grown a semiconductor light-emitting device of low threshold.

[Thirty-Third Mode of Invention]

As explained with reference to the previous mode there is a substantialrisk, when growing a semiconductor light-emitting device having anactive layer containing nitrogen, that the material containing Al isincorporated into the active layer containing nitrogen at the time ofgrowth thereof when the material containing Al is adsorbed on thesusceptor adjacent to the substrate before the growth of the activelayer. Thereby, the efficiency of optical emission is degraded. In orderto reduce this risk, the thirty-third mode of the present inventionprovides a detachable cover on the susceptor as the means for reducingthe adsorption of the material containing Al.

FIG. 66 is a diagram showing the example of the production apparatus ofsemiconductor light-emitting device according to the thirty-third modeof the present invention. It should be noted that FIG. 66 is a schematiclongitudinal cross-sectional view of the reaction chamber of the MOCVDapparatus as viewed from a lateral direction. In FIG. 66, those partscorresponding to the part explained previously are designated by thesame reference numerals and the description thereof will be omitted.

In, the example of FIG. 66, it will be noted that the reaction chamberis a longitudinal-type reactor and includes a substrate on which growthof a semiconductor light-emitting device is made and a susceptor holdingthe substrate.

In such a construction, the source gas introduced from source gas inletport 1314, causes a pyrolitic decomposition on the surface of thesubstrate 1312 held on the susceptor 1313, wherein the susceptor isheated to a high temperature by the resistance heater provided in thestage 1313 A located under the susceptor 1313, and there is caused agrowth of a semiconductor layer.

Meanwhile, in this second mode, the susceptor 1313 is covered with aremovable cover 1313C except for the part carrying the substrate 1302(see FIG. 67). This cover 1313 C is detachable in the growth chamber1311 without degrading the atmosphere, and it is possible to take outfrom growth chamber 1311. In this case, problems such as contaminationor oxidation of the substrate 1312 do not occur before and after themounting of the cover 1311. It is preferable that the cover 1313 C has astructure that covers substantially the entire surface of the susceptor1313, except for the part exposing the substrate 1312.

According to the present mode of the invention, the adsorption of theresidual Al species on the susceptor 1313 does not take place when thelayer containing Al susceptor 1313 is grown in the state covered withsaid cover 1313C.

Thus, it is possible to produce a high semiconductor light-emittingdevice of high efficiency of optical emission by using the productionprocess of the semiconductor light-emitting device and the productionapparatus of the semiconductor light-emitting device of each mode notedabove.

FIG. 68 is a diagram showing an example of the surface-emission laserdiode produced according to the production process of a semiconductorlight-emitting device and a production apparatus of a semiconductorlight-emitting device of the present invention. In FIG. 68, those partscorresponding to the parts explained previously are designated by thesame reference numerals and description thereof will be omitted.

FIG. 68 is referred to.

The surface-emission laser diode has a construction similar to the oneexplained with reference to FIG. 46 has a structure in which the n-typesemiconductor multilayer reflector 1352, the GaAs lower spacer layer1353, the GaInNAs/GaAs multiple quantum well active layer 1354, the GaAsupper spacer layer 1355, the AlAs layer 1356 and the p-typesemiconductor multilayer reflector 1357 are laminated consecutively onthe n-type GaAs substrate 1351.

Here, the n-type semiconductor multilayer reflector 1352 is formed of adistributed Bragg reflector in which an n-type GaAs high refractiveindex layer and an n-type Al_(0.8)Ga_(0.2)As low refractive index layerare laminated alternately. Similarly, the p-type semiconductormultilayer reflector 1357 is formed of a distributed Bragg reflector inwhich a p-type GaAs high refractive index layer and p-typeAl_(0.8)Ga_(0.2)As low refractive index layer are stacked alternately.

Further, the GaInNAs/GaAs multiple quantum well active layer 1354 has abandgap wavelength of the 1.3 μm band. The part from the GaAs lowerspacer layer 1353 to the GaAs upper spacer layer 1355 forms a λ cavity.

The above layered structure is mesa-etched in a cylindrical form untilit reaches the n-type semiconductor multilayer reflector 1352, and thereis formed a mesa structure having a diameter of 30 μm. Further, there isformed a current confinement structure by selectively oxidizing the AlAslayer 1356 from the sidewall exposed by the mesa etching so as to forman AlOx insulation region. In this case, electric current is confined tothe opening formed in the AlOx insulation region with a size of about 5μm φ and is injected into active layer 1354.

Further, a ring-shaped p-side electrode 1358 is formed on the surface ofthe p-type semiconductor multilayer reflector 1357, and the n-sideelectrode 1359 is formed on the rear side of the n-type GaAs substrate1351.

In the surface-emission laser diode of such a construction, the lightradiated in the GaInNAs/GaAs multiple quantum well active layer 1354 isamplified as it is reflected by the top and bottom semiconductormultilayer reflectors 1352 and 1357, and laser beam of the 1.3 μm bandis emitted in the direction perpendicular to the substrate 1351.

In the surface-emission laser diode of such a construction, theAlGaAs/GaAs stacked type reflector can most easily provide a highperformance reflector and can be used easily in view of the excellentelectric properties when used for the semiconductor multilayer reflector1352 on GaAs substrate 1351. In fact, a VCSEL of 0.85 μm band and the0.98 μm band that uses the AlGaAs/GaAs stacked type semiconductormultilayer reflector is already produced and marketed. Thus, in thesurface-emission laser diode formed on a GaAs substrate, thesemiconductor multilayer reflector of the AlGaAs/GaAs stacked type isthought an indispensable element. However, there has been a problem ofdegradation of quality of the active layer 1354 in the case asurface-emission laser diode using an active layer containing nitrogenis formed by an MOCVD process and the reflector 1352 is formed with theAlGaAs/GaAs stacking. Thus, it was not possible to obtain a lowthreshold device.

The process for growing the surface-emission laser diode of FIG. 68 isas follows.

First, the n-type semiconductor multilayer reflector 1352 is grown onthe substrate 1351. While growing the n-type semiconductor multilayerreflector 1352, the susceptor 1313 is covered with the cover 1313C. Withthis, adsorption of the Al species on the susceptor 1313 is almosteliminated and adsorption occurs mainly on the cover 1313C.

Next, the lower spacer layer 1353 and the active layer 1354 are grown.In this case, the cover 1313C is removed. The cover 1313C thus removedis moved outside the reaction chamber 1311. By removing the cover 1313C,the residual Al species are removed from the reaction chamber 1311together with the cover 1313C, and it becomes possible to prevent theresidual Al species from being incorporated in to the substrate bymaking a contact with the nitrogen source compound or the impuritycontained in the nitrogen source compound.

In the apparatus of this mode, it is possible to remove the cover 1313Cfrom the susceptor 1313 and move the same to the outside of the reactionchamber 1311 without degrading the atmosphere. Because of this, theprocess of removing the cover 1313C can be achieved anywhere after thegrowth of the layer containing Al has been completed but before thestart of growth of the active layer 1354.

For example, it is possible to conduct the process of removing the cover1313C between the growth of the lower spacer layer 1353 and the growthof the n-type semiconductor multilayer reflector 1352.

Thereafter, the upper part spacer layer 1355 and the p-typesemiconductor multilayer reflector 1357 are and the crystal growthprocess is terminated. When growing the p-type semiconductor multilayerreflector 1357, it is possible to provide the cover 1313 C once again.By doing so, adsorption of the residual Al species on the susceptor 1313can be prevented at the time of growth of the p-type semiconductormultilayer reflector 1357. Particularly, in the case of growing asemiconductor light-emitting device continuously, the materialcontaining Al and adsorbed on the susceptor when the p-typesemiconductor multilayer reflector 1357 has been grown, is desorbed fromthe susceptor at the time of the next growth. Thereby, there is aconcern that there may be an adversary influence to the active layer.Because of this, it is desirable to provide the cover 1313 C whengrowing the p-type semiconductor multilayer reflector 1357. By using theproduction apparatus and the process of the present invention as notedabove, it becomes possible to grow a surface-emission laser diode of lowthreshold and having the active layer 1354 of GaInNAs, and the like,even in the case of using a semiconductor multilayer reflector 1352 ofthe AlGaAs/GaAs stacking.

Thus, according to the production method and apparatus of asemiconductor light-emitting device of the present embodiment, in whichthere is provided a semiconductor layer containing Al between thesubstrate and the active layer containing nitrogen, there is provided aremovable cover on the susceptor holding the substrate so as to coverthe part except for the region on which the substrate is supported, whengrowing the active layer containing nitrogen and the semiconductor layercontaining Al respectively by the nitrogen compound source and the metalorganic Al source, such that the cover is mounted at the time of growingthe semiconductor layer containing Al and such that the cover is removedat the time of growing the active layer containing nitrogen. Here, theremovable cover 1313C has a mechanism for allowing mounting anddismounting in the state that the susceptor 1313 is loaded in thereaction chamber 1311.

[Thirty-Fourth Mode of Invention]

FIGS. 71A and 71B are the diagrams showing an example of the productionapparatus according to a thirty-fourth mode of the present invention. Itshould be noted that FIG. 71A is a schematic view of the cross-sectionaldiagram of the reaction chamber of the MOCVD apparatus as viewed from alateral direction. In the drawings, those parts corresponding to theparts described previously are designated by the same reference numeralsand the description thereof will be omitted. In the example of FIGS. 71Aand 71B, the reaction chamber is a lateral-type reactor.

In the apparatus of FIG. 71A, the growth chamber 1301 accommodatestherein the substrate 1302 on which growth of the semiconductorlight-emitting device is caused and the susceptor 1303 that holds thesubstrate 1302 thereon. The susceptor 1303 formed with carbon and isprovided with a depression for holding the substrate 1302.

Further, the cover 1303C is formed of quartz and is mounted detachablyon the susceptor 1303 (see FIG. 72).

The susceptor 1303 is designed so as to cause induction heating andcauses a pyrolitic decomposition of the source gas introduced from thesource gas inlet port 1304 on the surface of the substrate 1302 held onthe susceptor 1303, which in turn is heated, and there takes place agrowth of a semiconductor layer. The susceptor 1303 is installed on asupport rod 1303R and is movable between the reaction chamber 1301 andthe transportation chamber 1301A as shown in FIG. 71B. The susceptor1303 is removed from the support rod 1303C in transportation chamber1301A and the removed susceptor 1303 can be moved to and from thesubstrate holding chamber 1312 together with the substrate 1302 and thecover 1303C, and the like. The communication between each of thechambers 1301, 1301A and 1321 can be interrupted by a gate valve, andthe like, and the inside thereof can be adjusted to a desiredatmosphere. In the present invention, the cover 1303C has a shape so asto simply put on the susceptor 1303. Mounting and removal thereof isconducted as follows. The susceptor 1303 is transported from thereaction chamber 1301 to the transportation chamber 1301A. Thereafter,the susceptor 1303 and the substrate 1302 are removed from the supportrod 1303R and transported to the substrate holding chamber 1321. In thesubstrate preservation chamber 1321, it is possible to remove the coverby using a cover mount/dismount lever 1303CL as shown in FIG. 73.

In this apparatus, it is possible to grow the semiconductorlight-emitting device shown in FIG. 5 with the process as follows.

First, a first semiconductor layer 202 containing Al such as AlGaAs isgrown on the substrate 201. After the process of growing thesemiconductor layer 202 containing Al has been terminated, a GaAsintermediate layer 203 is grown to a midway point thereof. Next, thegrowth is interrupted once and the substrate 1302 corresponding to thesubstrate 201 and the susceptor 1303 are transported to the substrateholding chamber 1321. Then the cover 1303C is removed. Thereafter, it istransported again to the reaction chamber 1301 and growth of theremaining part of the intermediate layer 203 is conducted. Further, theactive layer 204 and the upper part intermediate layer 203 are grown,wherein the growth of the upper intermediate layer 203 is interrupted ata midway point thereof. After that, the growth is suspended and it istransported to the substrate holding chamber 1321. There, the cover1303C is mounted and is transported further to the reaction chamber1301. Thereby, the growth of the remaining part of the upperintermediate layer 203 is reduced. Further, the second semiconductorlayer 205 containing Al is conducted.

As the mounting and dismounting of the cover is conducted withoutopening the substrate holding chamber 1321 to the atmosphere by usingthe lever 1303CL, it is impossible to reduce the contamination oroxidation of the substrate.

According to such a process, it becomes possible to prevent theincorporation of the material containing Al being incorporated into theactive layer by causing a contact with the nitrogen compound sourcematerial or the impurity contained in the nitrogen compound sourcematerial, and it becomes possible to grow a semiconductor light-emittingdevice of low threshold.

In this embodiment, it is further possible to conduct the process ofmounting and dismounting the cover also in the case there is no covermount/dismount lever provided by modifying the embodiment. In this case,the process of mounting and dismounting the cover can be conductedmanually by opening the sample room to the atmosphere. As the substrateis opened to the atmosphere according to such an approach, there is apossibility of oxidation, In the present invention, the growth isinterrupted in the course of growth of GaAs, which forms theintermediate layer. Because GaAs is difficult to be oxidized as comparedwith AlGaAs, it is possible to minimize the influence of oxidation bythe atmosphere at the time of opening for a short period, provided thatGaAs, not AlGaAs, is exposed at the outermost surface. With this, theinfluence of exposure to the atmosphere is minimized.

Although the construction of manually mounting and dismounting the coverreceives the influence of exposure to the atmosphere, there is anadvantage in that the construction of the apparatus becomes extremelysimple due to the elimination of the lever for mounting and dismountingthe cover. With this, it is possible to apply a general MOCVD apparatusused at the present time. Thus, provided that the layout inside thereaction chamber allows, it is possible to conduct out the presentembodiment by merely providing a cover can be mounted and transported.Generally, an MOCVD apparatus is an extremely expensive apparatus andcannot easily apply a modification when the modification is a large one.However, the present invention enables to use the present invention withlow cost, without the need of large-scale modification. Further, in viewof the fact that the lever for mounting and dismounting the cover ismerely provided in the substrate-holding chamber 1321 and does notrequire extensive modification even in the case of incorporating themechanism, the implementation of the lever is not difficult.

[Thirty-Fifth Mode of Invention]

FIG. 74 shows the example of the MOCVD apparatus used with thethirty-fifth mode of the present invention.

FIG. 74 is referred to. The MOCVD apparatus includes a vacuum pump 2011,a growth chamber 2012, a wafer substrate 2013, a bubbler 2014, variouskinds of cylinders 2015, a hydrogen refining unit 2016, a mass-flowcontroller (MFC) 2017, and a gas supply control valve 2018.

FIG. 75 shows the construction of a GaInNAs system edge-emission laserproduced by the MOCVD apparatus of FIG. 74.

First, overall construction will be explained. The growth chamber(reaction chamber) 2012 is capable of being evacuated to low pressure bythe vacuum pump 2011, and a susceptor having a heating capability isprovided in the growth chamber 2012. Further, there are lines forproviding organic metal sources such TMG, TMA and TMI and also a line ofsupplying dimethyl hydrazine (DMHy) as a nitrogen source material,wherein these gases are supplied together with a carrier gas of H₂.Further, it can be seen that there are lines line for supplying AsH₃,H₂Se and also DMZn in the reaction chamber 12. H₂Se and DMZn are thesource gas lines for doping to n-type and p-type, respectively.

In many cases, the group III source material lines and the V groupsource material lines are gathered together separately and are suppliedto the reaction chamber 2012 as shown in the drawing, for improving thecontrol of the source supply rate and to prevent conjunction productoccurrence between different source materials.

Next, the process of film formation will be explained.

First, an n-type GaAs substrate (wafer substrate 2020) is set on thesusceptor, and the reaction chamber 2012 is evacuated. Further, thesusceptor is heated and TMG, TMA, AsH₃ and H₂Se are introduced into thereaction chamber to cause an epitaxial growth of an n-type AlGaAs film(21). Next, the growth process is interrupted and at least one of thegroup III source material line and the reaction chamber 2012 isevacuated. It is preferable that a pressure of 2.0× the 10² Pa or lessis attained in this time. More preferably, the pressure is 2.0×10⁻² Paor less. The vacuum evacuation is effective in the case conducted foronly one of the group III source material lines and the reaction chamber2012. However, a better effect is achieved when both are evacuated.Also, it is desirable to heat the group III source material lines andthe reaction chamber 2012 simultaneously to the vacuum evacuation.

Next, TMG, TMI, AsH₃ and DMHy are introduced into the reaction chamber2012 and a GaInNAs film 2022 is caused to grown epitaxially. Further,TMG, TMA and AsH₃ and DMZn are introduced into the reaction chamber 2012and a p-type AlGaAs film 2023 is caused to grow epitaxially. In thisway, a laminated film having a structure of p-type AlGaAs/GaInNAs/n-typeAlGaAs/n-type GaAs substrate is obtained. Finally, a p-side electrodepart 2024 and an n-side electrode part 2025 are formed and a lightemitting diode device is obtained.

According to this construction, there is provided the process ofevacuating the Al source supply line and the reaction chamber after thesemiconductor layer containing Al is grown. Therefore, the residual Alspecies are removed from the Al source supply line and the reactionchamber. Thus, even when the nitrogen source, which contains theimpurity (water, alcohol) reactive with the residual Al species and iseasily incorporated into the film, is supplied in the processthereafter, the problem of incorporation of oxygen originating from theimpurity together with Al is eliminated. Thus, it becomes possible toform a high-quality nitrogen containing group III–V compoundsemiconductor film containing little impurity and crystal defects. Withthis, it becomes possible to produce a device of high efficiency ofoptical emission and excellent reliability.

In the above process, it is possible to measure the concentration of theresidual Al species in any points between the vacuum pump and theorganic-metal Al source supply line during the process of evacuating atleast one of the organic-metal Al source supply line and the reactionchamber. With this, it becomes possible to measure the concentration ofthe residual Al species and evaluate the timing of terminating of thevacuum evacuation process.

The measurement of concentration of the residual Al species can beachieved by various means such as mass spectroscopy, infraredspectrophotometry, gas chromatography, and the like, wherein it is mostpreferable to use a mass spectroscopy in view of possibility of directconnection with a vacuum system and in view of high sensitivity. FIG. 74shows the example of connecting a quadruple mass spectrometer to thereaction chamber.

According to this construction, in which the concentration of theresidual Al species is measured, excellent reproducibility is achievedand the process loss time is eliminated. Further, it becomes possible toremove the residual Al species from the Al source material supply lineand the reaction chamber. Because of this, it is possible to obtain agroup III–V compound semiconductor film of high crystal quality,containing little defects and impurities and still containing nitrogenis obtained with excellent reproducibility and high efficiency. As aresult, it becomes possible to produce a light-emitting device of highoptical efficiency and high reliability with high efficiency andexcellent reproducibility.

Also, according to the present mode of the invention, the nitrogensource material of the group III–V compound semiconductor filmcontaining nitrogen includes at least hydrazines.

Here, hydrazines include the materials of hydrazine, monomethylhydrazine, dimethylhydrazine, buthylhydrazine, hydrazobenzene etc., andtakes the chemical formula of NR₂NR (R is hydrogen or alkyl group oraryl group).

NH₃ and also amines require the temperature of about 900° C. for formingactive species with sufficient concentration in view of highdecomposition temperature. Because of this, there tends to occurescaping of constituent element from the growth film. In the case of thegrowth film containing In, N, Ga, As, escaping of these atoms becomesparticularly distinct, and the crystal quality of the growth film isdeteriorated. Thereby, high-performance device is not obtained.

The decomposition temperature of hydrazines is low and takes the valueof about 500° C. Thus, active species can be formed with sufficientconcentration at low temperature and a high-quality good growth isobtained easily.

However, there is the problem that elimination of water content oralcohol is difficult in the case of hydrazines as compared with NH₃ oramines, and there is a tendency that hydrazines contain water or alcoholas impurity. Thus, it has been difficult to obtain a device havingsufficient characteristics and reliability as noted before.

In this construction, there is provided a process of evacuating the Alsource line and the reaction chamber after growing a semiconductor layercontaining Al. Accordingly, the residual Al species are removed from theAl source line and the reaction chamber. Thus, it becomes possible touse hydrazines, which tend to contain impurities (water content,alcohol) easily incorporated into the film by causing a reaction withthe residual Al species, as the nitrogen source material. Because ofthis, it becomes possible to obtain a nitrogen-containing group III–Vcompound semiconductor film of high crystal quality, containing littledefects or impurities and little deficiency of the constituent elements.Thereby, production of highly efficient and highly reliablelight-emitting device becomes possible.

In this mode of the present invention, there is also provided a laserdiode produced by the above process and uses the GaN system for thenitrogen-containing group III–V compound semiconductor film.

GaN, GaInN, GaPN, GaInPN, BBGaN, BGaInN, GaNSb, GaInNSb, and the likeare listed for the GaN material.

This GaN system material has a bandgap energy of ultraviolet light tovisible region and can be grown epitaxially on a single crystal ofα-Al₂O₃, β-Al₂O₃, h-ZnO, and the like, and also on the selectively grownGaN film. With regard to the selection growth GaN film, reference shouldbe made to S. Nakamura, et al., Appl. Phys. Lett. 72 (1998), pp. 211.

For the example of the semiconductor film containing Al, AlN, AlGaN, andthe like are listed. These materials, too, can cause an epitaxial growthon a single crystal such as α-Al₂O₃, β-Al₂O₃, h-ZnO or on theselectively grown GaN film by adjusting the composition thereof.

(Device Form)

Edge-emission type and surface-emission type are examples of the devicestructure of a laser diode.

In the case of edge-emission laser diode, it is classified into singleheterojunction type, double heterojunction type, separate-confinementheterojunction (SCH) type, and multiple quantum well structure (MQW)type, according to the type of the active layer. Further, according tothe type of the cavity, it is classified into Fabry-Perot (FP) type,distributed-feedback (DFB) type, and distribution Bragg reflector (DBR)type.

A surface-emission laser diode takes the construction to provide thelaser cavity perpendicularly to the substrate and emits the light in thedirection perpendicularly to the substrate. Reflectors such as asemiconductor multilayer reflector or dielectric multilayer reflector ormetal reflector of high reflectance are provided on the substrate and onthe surface, and an active layer is provided between these reflectors.Further, a spacer layer is provided between the active layer and the tworeflectors.

Further, in many case, there is provided a current confinement structurethat confines the current path in the region near the active layer so asto reduce the threshold current, to cause a single-mode oscillation, andto prevent non-optical recombination at the side wall.

A surface-emission laser can be integrated in a two-dimensional array.Further, because of the narrow divergent angle of the output opticalbeam (about 10°), it is possible to couple with an optical fiber easily.In addition, inspection of the device can be made easily. Therefore, asurface-emission laser diode is thought as the device particularlysuited for constructing an optical transmission module (opticalinterconnection apparatus) of parallel-transmission type. Although theimmediate application of optical interconnection apparatus is limited tooptical fiber communication of short distance, or parallel connectionbetween computer sets or between boards in a computer, it is alsoexpected that the optical interconnection apparatus is used in alarge-scale computer network in the future,

Hereinafter, the case of producing a SCH type laser diode that uses anInGaN film as the active layer by using the MOCVD apparatus of FIG. 76will be explained. Those parts explained previously are designated bythe same reference numerals and the description thereof will be omitted.

In the construction of FIG. 76, the NH₃ gas in the gas cylinder 2015 isused as the nitrogen source material,

FIG. 77 is a diagram showing the example of the edge surface-emissionlaser produced by using the MOCVD apparatus of FIG. 76.

Hereinafter, explain will be made with reference to FIGS. 76 and 77.

First, TMA, TMG, NH₃ and SiH₄ (silane) are introduced on a singlecrystal substrate 2031 of α-Al₂O₃ or β-SiC, h-ZnO, or on a selectivelygrown GaN film 2033, and there is caused a growth of an N-AlGaN claddinglayer 2034. After this, the growth is interrupted and the Al source lineand the reaction chamber are evacuated. After reaching the pressure2.0×10⁻⁴, TMG, NH₃ and SiH₄ (silane) are introduced and n-GaN guidelayer 2035 is formed. Next, TMI, TMG, and NH₃ are introduced and ann-GaN active layer 2036 is formed. Further, TMG, NH₃ and DMZn areintroduced and an n-GaN guide layer is formed. Next, TMA, TMG, NH₃ andDMZn are introduced, and a p-AlGaN cladding layer 2037 is formed.Further, a p-side electrode part 2039 and an n-side electrode part 2040are provided, and there is formed a cavity parallel to the film surfaceby a dry etching process. With this, an edge-surface emission laserdiode is produced.

By injecting holes into the p-side cladding layer 2037 and electronsinto the N-cladding layer 2034, there is caused optical radiation in theactive layer.

[Thirty-Sixth Mode of Invention]

Next, the case of producing a surface-emission laser diode that uses anactive layer of a quantum well structure (QW) by using the MOCVDapparatus of FIG. 76 will be shown, in which it should be noted that anInGaN film is used for the quantum well layer and a GaN film is used forthe barrier layer.

FIG. 78 is a diagram showing the example of the edge surface-emissionlaser that produced by using the MOCVD apparatus of FIG. 76.

Hereinafter, explanation will be made with reference to FIGS. 76 and 78.

First, TMA, TMG and NH3 are introduced on a single crystal substrate2041 of α-Al₂O₃, β-Al₂O₃ or h-ZnO, or on a selectively grown GaN film2043. With this, a semiconductor multilayer reflector 2044 formed of 20pairs or more of AlN/GaN are grown. Thereafter, the growth isinterrupted and the Al source line and the reaction chamber areevacuated. Next, after reaching the pressure of 2.0×10⁻⁴ Pa, TMG, NH₃and SiH₄ are introduced and an n-type GaN contact layer 2045 is formed.Further, an n-type GaN spacer layer 2046 is formed. Further, byintroducing TMI, TMG and NH₃, an InGaN/GaN quantum well (QW) activelayer 2047 is formed. Further, by introducing TMG, NH3, SiH₄ and DMZn, ap-type GaN spacer layer 2048 is formed. Also, a p-type GaN contact layer2049 is formed. Next, a semiconductor multilayer reflector 2050 isformed by introduces TMA, TMG and NH₃ such that 20 or more pairs ofAlN/GaN are formed.

It is also possible to provide a current confinement part by forming aninsulation region 2051 in the vicinity of the active layer vicinity byan ion implantation process of proton or oxygen.

Next, a p-side electrode part 2052 and an n-side electrode part areformed, and a surface-emission laser diode having a cavity structureperpendicular to the film surface is produced.

By injecting holes and electrons to the p-type semiconductor multilayerreflector and to the n-type semiconductor multilayer reflectorrespectively, there is caused a radiation in the active layer.

According to this construction, there is provided a process ofevacuating the Al source line and the reaction chamber after thesemiconductor layer containing Al is grown. Because of this, theresidual Al species are removed from the Al source line and the reactionchamber. Thereupon, it becomes possible to form an active layer of anitrogen-containing InGaN system material of high crystal quality andcontaining little impurities or defects, even in the case a nitrogensource material containing impurity (water content, alcohol, and thelike), which tends to be incorporated into the film by reacting withresidual Al species, is used.

Thus, it is possible to produce a short wavelength laser having anoscillation wavelength in the ultraviolet to visible regions with highyield such that the laser diode has the feature of low thresholdcurrent, high efficiency of optical emission, high reliability andexcellent temperature characteristics.

For the InGaN system material of such a laser diode, it is possible touse GaNAs, GaInNAs, GaInNAsSb, GaInNP, GaNP, GaNAsSb, GaInNAsSb, InNAs,InNPAs, and the like.

In these materials, it is possible to achieve a lattice matching withGaAs by adjusting the composition thereof, and it is possible to causean epitaxial growth on a GaAs substrate.

The examples of the semiconductor film containing Al include AlGaAs,AlAs, AlGaInP, AlGaAsP, AlInP, AlGaIns, AlGaInAsP, and the like. Thesematerials, too, can achieve lattice matching with GaAs by adjusting thecomposition thereof, and can grow epitaxially on the GaAs substrate.

The laser that uses the material of the InGaN system excels in thetemperature characteristics, and in addition, it provides anadvantageous feature of compatibility with the quartz optical fiber inview of the long oscillation wavelength band of 1.1 μm or more. Thus,the device is thought to becomes an indispensable device opticaltelecommunication systems or in optical interconnection betweencomputers or chips, or in optical computing.

It should be noted that an especially high crystal quality is requiredfor the constituent films of a laser diode. In the construction in whicha semiconductor layer containing Al having excellent characteristic withregard to confinement of light and electrons is provided between theGaAs substrate and the active layer of the InGaN system material, it hasbeen difficult to obtain a laser of high characteristics and highreliability.

[Thirty-Seventh Mode of Invention]

Next, the example of producing a SCH type edge-emission laser diode thatuses a GaInNAs film for the active layer by using an MOCVD apparatus ofFIG. 74 will be explained.

FIG. 79 shows the example of the edge-emission laser diode produced byusing the MOCVD apparatus of FIG. 74.

Hereinafter, explanation will be made referring to FIG. 74 and FIG. 79.

First, TMG, TMA, AsH3 and H₂Se are introduced on a GaAs substrate 2055and an n-type AlGaAs cladding layer 2056 is grown epitaxially. Afterthat, the growth is interrupted and an Al source line and the reactionchamber are evacuated. After reaching the pressure of 2.0×10⁻⁴ Pa, TMGand AsH³ are introduced and a GaAs guide layer 2057 is formed. Further,TMG, TMA, TMI, AsH₃ and also DMHy are introduced and a GaInNAs activelayer 2058 is formed. Further, TMG and AsH₃ are introduced and a GaAsguide layer 2059 is formed. Further, by introducing TMG, TMA, AsH₃, andDMZn, a p-type AlGaAs upper cladding layer 2060 is formed.

On the stacked structure thus formed, a p-side stripe electrode 2061 andan n-side electrode part 2062 are formed, and there is obtained anedge-emission laser diode having a cavity parallel to the film surfaceby a cleaving process.

According to the present construction, there is provided a process ofevacuating the Al source line and the reaction chamber after thesemiconductor layer containing Al is grown. Because of this, theresidual Al species of the Al source material are removed from thesupply line and the reaction chamber. Thereupon, a nitrogen-containingactive layer of the GaNAs system having high crystal quality and littleimpurities can be formed even in the case of using a source materialcontaining impurity (water content, alcohol, and the like) that tends toreact with the residual Al species and easily incorporated into thefilm.

Thereby, it is possible to obtain a long wavelength laser having anoscillation wavelength suitable for use in optical telecommunicationwith high yield. The laser diode has high efficiency of opticalemission, high reliability and low threshold current.

[Conventional Art]

The present invention also provides a surface-emission laser having atleast one semiconductor multilayer reflector of theAlxGa1-xAs/AlyGa1-yAs (0≦y<x≦1) structure.

For the reflector of a surface-emission laser, a semiconductordistributed Bragg reflector in which a low refractive index layer andhigh refractive index layer are stacked alternately is used widely, inview of the capability of being formed together with the active layerregion with high control precision and in view of the capability ofcausing to flow the carriers for driving the laser. As for the materialof the semiconductor distributed Bragg reflector, the material thatachieves lattice matching with the substrate for avoiding latticerelaxation and at the same time not absorbing the light produced in theactive layer (generally the material of a wide bandgap than the activelayer), is used.

The reflectance of the reflector has to be extremely high, higher than99%. The reflectance can be increased by increasing the number of thestacks therein. However, when the number of the stacks is increased, theproduction of the surface-emission laser diode becomes difficult.Because of this, the refractive-index difference between the lowrefractive index layer and the high refractive index layer should be aslarge as possible. The system of AlGaAs has end-components of AlAs andGaAs. The lattice constant thereof is almost the same as that of GaAsused for the substrate and a large refractive-index difference can besecured by adjusting the composition. Thereby, it is possible to obtaina high reflectance with fewer stacks. Because of this, it isadvantageous to use the semiconductor multilayer mirror of theAl(Ga)As/GaAs structure, more generally the AlxGa1-xAs/AlyGa1-yAs(0≦y<x≦1) structure for the reflector of the surface-emission laser.

However, it has been not possible to obtain sufficient efficiency ofoptical emission, when an Al(Ga)As/GaAs semiconductor multilayer mirroris grown as a reflector of a surface-emission laser.

As demonstrated before by experiments, this is because the materialcontaining Al is chemically very active. In other words, there is atendency that crystal defects originating from Al are formed. As aresult, the Al source or Al source reactants remaining in the reactionchamber during the growth of the active layer including the GaNAs systemmaterial react with the water content or alcohol in hydrazine and areincorporated into the crystal. The Al species thus incorporated form acrystal defect forming the non-optical recombination, and because ofthis, the efficiency of optical emission has been degraded.

Because of this, Japanese Laid-Open Patent Application 08-340146official gazette or Japanese Laid-Open Patent Application 07-307525official gazette proposes to construct a semiconductor distributed Braggreflector from GaInP or GaAs not containing Al. However, therefractive-index difference between GaInP and GaAs is only about half ofthe refractive-index difference between AlAs and GaAs. Because of this,it is inevitable that the stacking number of the reflector is increasedsignificantly. As a result, the production becomes difficult and theyield falls off. Also, there arise problems such as increase of deviceresistance, long time needed for the device production and increase ofthe total thickness of the surface-emission laser. This causes theproblem of difficulty of providing electric interconnection.

[Thirty-Ninth Mode of Invention]

Next, an example of producing a surface emission laser diode having anactive layer of a quantum well structure (QW), which uses a GaInNAs filmas the well layer and GaAs as the barrier layer by the MOCVD apparatusof FIG. 74 will be described.

FIG. 80 is a diagram showing the construction of the surface emissionlaser diode produced by using the MOCVD apparatus of FIG. 74.

FIG. 80 is referred to. A semiconductor multilayer reflector 2066 ofn-type AlGaAs/n-type GaAs including 25 or more pairs are grownepitaxially on a GaAs substrate 2065 by introducing TMG, AsH₃, H₂Se, andthe like.

After this, the growth is interrupted and the Al source line and thereaction chamber are evacuated. After reaching the pressure of 2.0×10⁻⁴Pa, TMG, AsH₃ and H₂Se are introduced and an n-type GaAs spacer layer2067 is formed. Next, by introducing TMG, TMA, TMI, AsH₃, and DMHy, aGaInNAs/GaAs quantum well (QW) active layer 2068 is formed. Next, byintroducing TMG, AsH₃ and DMZn, a p-type GaAs spacer layer 2067 isformed. Next, a semiconductor multilayer reflector 2069 formed of 20 ormore pairs of p-type GaAs, and the like, is formed by introducing TMG,TMA, AsH₃ and DMZn. Furthermore, by providing a p-type contact layer2070, the epitaxial films constituting the laser is formed.

Further, there can be a case in which an insulating AlxOy film is formedby oxidizing the AlAs film in the vicinity of the active layer, or aninsulation region 2071 is formed in the vicinity of the active layer byan ion implantation process of proton or oxygen, so as to form a currentconfinement part.

Next, a p-type electrode part 2072 and an n-type electrode part 2073 areformed. With this, the surface emission laser diode having a cavitystructure perpendicular to the film surface is formed.

According to this construction, the process of evacuating the Al sourceline and the reaction chamber is provided after the growth of theAlxGa1-xAs/AlyGa1-yAs (0≦y<x≦1) semiconductor multilayer reflector.Because of this, the residual $O species are removed from the Al sourcematerial supply line and the reaction chamber, and it becomes possibleto form an active layer of the GaNAs system film of high crystal qualityand little impurities or defects. Therefore, it is possible to obtain along wavelength surface-emission laser having a simple construction, lowthreshold and high yield, with a low cost process. Such a longwavelength surface-emission laser has a low device resistance, low valuecurrent, high efficiency of optical emission, high reliability and alsoexcellent temperature characteristics. Further, it has an oscillationwavelength suitable for use in optical telecommunication.

[Fortieth Mode of Invention]

A fortieths mode of the present invention provides a telecommunicationsystem in which the surface-emission laser diode of the thirty-eighthmode is used as the light source.

The construction of this optical telecommunication system will beexplained with reference to the drawings.

FIG. 81 shows an example of the parallel transmission type opticaltelecommunication system that uses the surface-emission laser diode.

FIG. 81 is referred to.

In this mode, the signals from the surface-emission laser diodes 2075are transmitted to the photodetection devices 2077 simultaneously byusing plural optical fibers 2079.

FIG. 82 is an example of the multiple-wavelength transmission typeoptical telecommunication system that uses the surface-emission laserdiode.

FIG. 82 is referred to. The optical signals from GaInNAssurface-emission lasers 2080 of plural, different oscillationwavelengths are injected to an optical fiber 2086 via an opticalmultiplexer 2081. Thereby, the plural optical signals of differentwavelengths are multiplexed and injected into a single optical fiber fortransmission. The optical signal thus transmitted is divided into pluraloptical signals that of different wavelengths via an opticaldemultiplexer 2084 connected to various units of the destination stationand the optical signals reach respective plural photodetection devices2083 through the respective optical fibers.

According to the present invention, the optical telecommunication systemis constructed by using a long-wavelength laser having the features oflow device resistance, low threshold current, high-efficiency of opticalemission, high reliability, excellent temperature characteristics andoscillation wavelength suitable for use in optical telecommunication andproduced with high yield at low cost and with a simple construction.Thus, it is possible to obtain an optical telecommunication system ofhigh reliability and high performance, having a simple construction notrequiring a cooling device for the optical source part.

<Embodiment 17>

FIG. 83 shows the construction of an edge-emission laser diode ofEmbodiment 17 that uses the MOCVD apparatus of FIG. 76.

FIG. 76 and also FIG. 83 are referred to. A heatable susceptor isprovided in a reaction chamber 2012 evacuated to low pressure reductionby a vacuum pump C. Further, lines for supplying TMG, TMA, TMI and NH₃to the reaction chamber while using an H₂ gas as the carrier gas areprovided. Further, lines for supplying SiH₄ (silane) and Zn(CH₃)₂ (DMZn)to the reaction chamber 2012 are provided.

By using the low-pressure MOCVD apparatus, a buffer layer 2091 of GaN iscaused grow on a sapphire c face single crystal board 2090 in theamorphous state at the substrate temperature of 550° C. with thethickness of 20 nm. Next, a GaN foundation layer 2092 is caused to growat the substrate temperature of 1050° C. with the thickness of 2 μm.Next, the sample is taken out from the MOCVD growth chamber into theatmosphere and an SiO₂ film 2093 is grown by a CVD process with thethickness of 0.1 μm. Further, a stripe window of 4 μm width is formed onthe SiO₂ film 2093 with the period of 11 μm by photolithography and wetetching process.

Further, the sample is again placed in the MOCVD growth chamber and aselective growth of an n-type GaN film 2094 is conducted on this maskpattern at the substrate temperature of 1050° C. Thereby, a GaN film iscaused to grow on the mask pattern from the buffer GaN layer 2092 in thelateral direction and an excellent single crystal film obtained withlarge area is obtained. Such a growth film is called selective growthfilm or ELOG (epitaxially laterally overgrown GaN substrate) substrate.

Next, by introducing TMG, NH₃ and SiH₄, an n-type GaN contact layer 2095is grown. Next, TMA, TMG, NH₃ and SiH₄ are introduced and an n-typeAlGaN cladding layer 2096 is grown. Next, by introducing TMG, NH₃ andSiH₄, an n-type GaN guide layer 2097 is grown.

Next, the growth process is interrupted and the Al source line and thereaction chamber are evacuated until it reaches the pressure of 2.0×10⁻⁴Pa or less by monitoring the indication of the ionization vacuum gauge.At this time, simultaneously to the vacuum evacuation, the group IIIsource line and the reaction chamber are heated to 100° C.–150° C.

Next, by introducing TMI, TMG and NH₃, a triple MQW active layer 2098 ofIn_(0.02)Ga_(0.98)N/In_(0.15)Ga_(0.85)N is grown. Next, by introducingTMG, NH₃ and DMZn, a p-type GaN guide layer 2099 is grown. Next, byintroducing TMA, GMG, NH₃ and DMZn, a P-type AlGaN cladding layer 2100is grown. Next, by introducing TMG, NH₄ and DMZn, a p-type GaN contactlayer 2101 is grown.

Next, a laser device processing process is conducted and a ridge-stripelaser is obtained.

The threshold current of the device thus produced was 60 mA in the caseof the continuous oscillation under room temperature. In theridge-stripe laser of the same construction produced without the growthinterrupt process for comparative example, it was confirmed that thethreshold current was 80 mA in the case of continuous oscillation underroom temperature.

It should be noted that there is conducted an evacuation process in theAl source line and the reaction chamber after growth of the n-type AlGaNcladding layer. Thus, the residual Al species are removed from the Alsource line and the reaction chamber. Thus, even when NH₃, which tendsto contain impurity (water content, alcohol etc.) that reacts with theresidual Al species and being incorporated into the film, though not soextensively as in the case of hydrazines, is introduced next step toform an MQW active layer of In_(0.02)Ga_(0.98)N/In_(0.15)Ga_(0.85)N, ahigh-quality active layer containing little defects or impurities isobtained. Because of this, it becomes possible to produce a ridge-stripelaser edge surface-emission laser capable of conducting room temperaturecontinuous oscillation with low threshold current.

<Embodiment 18>

FIG. 84 is a diagram showing the construction of an edge-emission laserdiode produced by using the MOCVD apparatus of FIG. 76.

FIG. 76 and FIG. 84 are referred to. The MOCVD apparatus includes aheatable susceptor in the reaction chamber 2012 that is evacuated to lowpressure by an evacuation steam system C including a vacuum pump.Further, it has lines for supplying gases of TMG, TMA, TMI, MMHy(monomethylhydrazine), AsH₃, PH₃, SeH₂, and Zn(CH₃)₂ to the reactionchamber together with an H₂ gas as the career gas. These gases areevacuated by the source gas evacuation system C having a rotary pump.Further, a high vacuum evacuation system (not shown) including a turbomolecular pump is connected to the reaction chamber.

Next, explanation will be made on the film formation process.

First, an N-type GaAs substrate 2110 cleaned with an HCl solution isheld on a susceptor. Next, the reaction chamber 2012 is evacuated andthe temperature of the susceptor is increased. Thereafter, TMG, TMA andAsH₃ are supplied to the reaction chamber and an n-type AlGaAs lowercladding layer 2111 is grown. Next, the growth process is interrupted.Further, the Al source line and the reaction chamber are evacuated untilthe pressure reading of the ionization vacuum gauge becomes 2.0×10⁻⁴ Paor less. At this time, the group III line and the reaction chamber 2012a are heated to 100–150° C. simultaneously to the vacuum evacuation.

Next, TMG, AsH₃ and GaAs are introduced and the guide layer 2112 isgrown. Next, TMG, TMA, TMI, AsH₃ and MMHy are introduced and GaInNAsactive layer 2113 is grown. Next, TMG and AsH₃ are introduced and a GaAsguide layer 2114 is grown. Next, TMG, TMA, AsH₃ and DMZn are introducedand a p-type AlGaAs upper cladding layer 2115 is grown. Further, byproviding a p-type GaAs contact layer, the epitaxial films constitutingthe laser are formed.

After this, an SiO₂ insulation film is formed, and after removing theSiO₂ film in a stripe form, a p-type electrode film 2116 is deposited byan evaporation deposition process. Next, an n-type electrode film 2117is deposited on the rear surface of the substrate. Finally, a cavity isformed parallel to the film surface by a cleaving process, and anedge-emission laser diode of broad stripe SCH structure is obtained.

In the construction of FIG. 84, the Al concentration in the active layer2098 was 1×10¹⁸ cm⁻³ or less and the oxygen concentration in the activelayer was 2×10¹⁷ cm⁻³ or less. Also the threshold current was 30 mA inthe case of continuation oscillation under room temperature.

As a comparative example, a broad stripe laser of the same constructionwas formed by a continuous process, without discontinuing the growth andconducting the evacuation of the Al source line and the reactionchamber. In this case, Al of 2×10¹⁹ cm⁻³ or more and oxygen of 2×10¹⁸cm⁻³ or more were incorporated into the active layer. Further, it wasconfirmed that the threshold current is remarkably large and had thevalue of 300 mA or more in the case of the continuation oscillationunder room temperature.

In the present invention, the residual Al species are removed from theAl source line and the reaction chamber because of the vacuum evacuationof the Al source line and the reaction chamber conducted after thegrowth of the n-type AlGaAs cladding layer. Because of this, a GaInNAsactive layer of high crystal quality characterized by little defects andimpurities obtained even in the case the growth of the GaInNAs activelayer is conducted growth in the next process, by introducing MMHy oflow decomposition temperature but containing impurities (water, alcohol,and the like) that tend to reacts with the residual Al species and tendto be incorporated into the film.

In the present embodiment, it becomes possible to produce a broad stripeedge surface-emission laser capable of continuous oscillation at roomtemperature possible with lower threshold current.

<Embodiment 19>

FIG. 84 shows the construction of an edge-emission laser diode producedby using the MOCVD apparatus of FIG. 76. In the present invention, aquadruple mass spectrometers (QMS) 2011 is connected to the reactionchamber 2012 via a valve in the MOCVD apparatus of FIG. 76 explainedwith reference to Embodiment 17. Further, DMHy (dimethylhydrazine) isused as the nitrogen source material.

FIG. 85 shows the construction of a surface emission laser diodeproduced by using the MOCVD apparatus of FIG. 76.

Hereinafter, the film formation process will be explained with referenceto FIG. 76 and FIG. 85.

First, an n-type GaAs substrate 2120 cleaned with an HCl solution at thesurface thereof is held on the susceptor. Next, the reaction chamber2012 is evacuated to a low pressure, and TMG, TMA and AsH₃ (arsine) aresupplied to the reaction chamber 2012 after increasing the temperatureof the susceptor. Next, the lower part semiconductor multilayer mirrorBragg reflector (lower part DBR) 2121 formed of 28 pairs of n-typeAlGaAs/n-type GaAs is grown.

Next, the growth process is interrupted and the Al source line and thereaction chamber are evacuated. At this time, the Al source line and thereaction chamber are heated to 100–150° C. simultaneously to the vacuumevacuation process. When the output current peak of the QMS forAl(CH₃)₃+(m/e72) has become smaller than a specified value, TMG, AsH₃and SeH₂ are introduced and the n-type GaAs spacer layer 2122 is grown.Next, TMG, TMA, TMI, AsH₃ and DMZn are introduced to grow the doublequantum well active layer 2123 formed of GaInNAs. Further, byintroducing TMG, AsH₃ and DMZn, a p-type GaAs spacer layer 2124 isgrown. Further, by introducing TMA, AsH₃ and DMZn, a p-type AlAsselective oxidation layer 2125 is grown. Further, the upper part DBR2126 consisting of 23 pairs of the p-type AlGaAs/p-type GaAs structuresis grown by introducing TMG, TMA, AsH₃ and DMZn. Furthermore, byintroducing TMG, AsH₃ and DMZn, a p-type GaAs contact layer 2127 isgrown. With this, an epitaxial growth multilayer film layered structureconstituting the laser diode is obtained.

Next, oxidization of the selective oxidation AlAs film 2125, exposed atthe semiconductor pillar sidewall, is conducted by using a water vapor,starting from the above-mentioned exposed sidewall. With this, theabove-mentioned AlAs film 2125 is converted to an AlxOy insulation filmwhile leaving the current path having a cross-sectional area of about 25μm²

Next, a non-photosensitive polyimide 2128 is applied by a spin coatingprocess, followed by a curing process at 350° C., so that the heightfrom the etched base becomes 4.0 μm. Next, a resist film is applied.Further, the above-mentioned polyimide film in the region of the 28μm×28 μm of the above-mentioned semiconductor pillar surface is removedby an RIE etching that uses lithography and an oxygen gas.

Next, an n-type electrode 2129 and a wiring part are formed on a part ofthe top surface of the semiconductor pillar excluding the optical windowand also on the polyimide, by way of evaporation deposition process anda lift off process. Finally, an n-type electrode 2130 is formed on therear surface of the substrate and a long wavelength surface-emissionlaser is obtained.

In the construction of FIG. 85, the Al concentration of the active layer2123 is 2×10¹⁸ cm⁻³ or less and the oxygen concentration was 3×1017-cm3or less. Further, the threshold current was 0.8 mA in the case ofcontinuation oscillation under room temperature.

For the purpose of comparison, a long wavelength surface-emission laserof the same construction was produced by a continuous process withoutconducting the vacuum evacuation process of the Al source line and thereaction chamber by the interruption of the growth. In this case, Al of3×10¹⁹ cm⁻³ or more of and oxygen of 2×1018 cm⁻³ or more wereincorporated into the active layer, and the threshold current was 4 mAor more in the continuation oscillation under room temperature.

In the present embodiment, the vacuum evacuation of the Al source lineand the reaction chamber 2012 is conducted after the growth of the lowerpart DBR consisting of 28 pairs of n-type AlGaAs/n-type GaAs. With this,the remaining Al species are from the Al source material supply line andthe reaction chamber 2012. Because of this, a high GaInNAs active layerof high crystal quality and containing little defects or impurities isobtained, the growth of the GaInNAs active layer is conducted byintroducing DMHy, which, while having a low decomposition temperature,tends to contain impurities (water, alcohol, and the like) incorporatedinto the film by causing a reaction with the residual Al species. Withthis, it becomes possible to produce a long wavelength surface-emissionlaser having a low threshold current and capable of conducting a roomtemperature continuation oscillation.

[Forty-First Mode of Invention]

FIG. 86 is a schematic diagram the MOCVD growth apparatus used in theforty-first mode of the present invention to grow a GaInNAssurface-emission type laser diode. In FIG. 86, those parts correspondingto the parts explained previously are designated by the same referencenumerals.

Although FIG. 86 has a construction resembles to the conventional MOCVDgrowth apparatus explained with FIG. 2 previously, there exists adistinction in that there are provided two gas line systems for groupIII gases in the apparatus of FIG. 86.

In more detail, there are provided bubblers 14#1 and 14#2 holding TMGand also TMA to the above-mentioned first group III gas line A11 in theapparatus of FIG. 86. Further, TMG and TMI bubblers 14#3 and 14#4 areprovided to the above-mentioned second group III gas line A12. Thus, thesemiconductor layer containing Al is supplied by using the group III gasline A11. On the other hand, the semiconductor layer containing nitrogenis grown by supplying the group III gas line A12.

Thus, by using plural group III gas lines, it becomes possible to supplya nitrogen source to the growth chamber without using the line used forsupplying the Al source material for growing the semiconductor layercontaining Al.

It is preferable in the MOCVD apparatus of FIG. 86 to stop the supply ofthe source material from the group III gas line A11 at the time ofgrowing the semiconductor layer containing nitrogen. Further, it ispreferable not to supply the carrier gas during such an interval.

By this method, the Al concentration in the active layer containingnitrogen is reduced to 1×10¹⁹ cm⁻³ or less, and it became possible tooscillate the semiconductor light-emitting device at room temperaturecontinuously. Furthermore, an optical emission characteristicsequivalent to the case the active layer is formed on a semiconductorlayer not containing Al was achieved by reducing the Al concentration inthe active layer containing nitrogen to the level of 2×10¹⁸ cm⁻³ orless.

It was confirmed that the broad stripe laser thus was obtained has thethreshold current similar to that shown in Table 4 previously.

[Forty-Second Mode of Invention]

In the present embodiment, an MOCVD apparatus of the constructionsimilar to that of FIG. 86 is used. However, there is a feature in thatthe inlet port of the group III material source gas to the reactionchamber is constructed in the form of at least double pipe structure.

In the case there are plural group III source gas lines provided to thereaction chamber together with plural source gas inlet ports, there canbe unfavorable cases of different film thickness distribution and thelike, for different layers, caused as a result of difference ofpositions of the gas inlet port.

Contrary to this, the change of distribution of the film thickness andthe like, for each of the layers can be minimized when the inlet port ofthe group III source gases into the reaction chamber is configured inthe double pipe structure, in view of the fact that the supply of thegases is made from substantially the same point.

GaNAs, GaInNAs, InNAs, GaAsNSb, GaInNAsSb, and the like, are examples ofthe semiconductor layer containing nitrogen. Explanation will be madebelow about GaInNAs. By adding N to GaInAs having a lattice constantlarger than that of GaAs, GaInNAs can achieve a lattice matching toGaAs.

With this, the bandgap is reduced and optical emission at the 1.3 μm or1.55 μm band becomes possible. Because it is a material system matchingwith a GaAs substrate, it is possible to use a wide gap material such asAlGaAs or GaInP for the cladding layer.

Further, the bandgap becomes small as shown above by the addition ofnitrogen. The energy level of the conduction band as well as the energylevel of the valence band are shifted in the lower energy side. Thereby,a very large band discontinuity is achieved in the conduction band atthe heterojunction. As a result, it is possible minimize the temperaturedependence of the laser operational current.

Further, the surface-emission laser diode is advantageous in view ofsmall size and low electric power consumption and in view of thecapability of two-dimensional integration suitable for the paralleltransmission. It is difficult to obtain the performance suitable forpractical use in a surface-emission type laser diode as long as theconventional GaInPAs/InP system is used. By using the GaInNAs system, onthe other hand, it becomes possible to use a semiconductor multilayerdistributed Bragg reflector of the Al(Ga)As/(Al)GaAs system or a currentconfinement structure formed by selective oxidation of AlAs, which isalready used successfully with the 0.85 μm band surface-emission typelaser diode, and the like, constructed on a GaAs substrate. Thereby, apractical surface-emission laser diode can be formed.

In order to achieve this, improvement of crystal quality of the GaInNAsactive layer, reduction of resistance of the multilayer reflector,improvement of crystal quality and control of the multiple layerstructure forming the surface-emission laser diode, are important.According to the production method of the present mode of the invention,it becomes possible to realize a surface-emission layer diode having alow resistance, operable at low drive voltage, having high efficiency ofoptical emission, low threshold current and excellent temperaturecharacteristics, easily with low cost. The surface-emission type laserdiode of the present embodiment can be used as an optical source of anoptical transmission module or optical transmission/reception module. Byusing such a surface-emission laser diode element having low resistance,low drive voltage, low threshold current and excellent temperaturecharacteristics, it becomes possible to realize a low-cost opticaltransmission module or optical transmission/reception module that doesnot require a cooling device. Further, by using such a surface-emissionlaser diode of low resistance, low drive voltage, low threshold currentand excellent temperature characteristics thus formed, it becomespossible to realize a low-cost optical telecommunication system such asoptical fiber transmission system, optical interconnection system, andthe like.

<Embodiment 20>

Hereinafter, explanation will be made about a GaInNAs surface-emissiontype laser diode according to Embodiment 20 of the present invention.

FIG. 87 is a diagram showing the structure of the GaInNAssurface-emission type laser diode according to Embodiment 20 of thepresent invention.

As shown in FIG. 87, the surface-emission laser diode of the presentembodiment includes, on an n-type GaAs substrate 2201 having a (100)surface orientation and a size of 2 inches, an n-type semiconductordistributed Bragg reflector (lower semiconductor Bragg reflector: orsimply lower part reflector) 2202 that consists of a periodicalstructure in which an n-type AlxGa1-xAs (x=0.9) and an n-type GaAs, eachhaving an optical film thickness of 1/4 times the oscillation wavelengthare stacked alternately for 35 times. An undoped lower GaAs spacer layer2203 is formed thereon. Further, a multiple quantum well active layer2204 consisting of three GaxIn1-xNyAs1-y quantum well layers and alsoGaAs barrier layers, is formed on the spacer layer 2203. Further, anundoped upper GaAs spacer layer 2205 is formed on the multiple quantumwell active layer 2204.

Further, a p-type semiconductor distributed Bragg reflector 2206 isformed on the spacer layer 2205. The upper reflector 2206 is constructedof a periodical structures of 25 periods, in which there is provided alow refractive index layer having an optic film thickness of 3λ/4 suchthat an AlAs selective oxidizing layer 2208 is sandwiched with a pair ofAlGaAs layers. Further, a GaAs layer having an optical thickness of λ/4is formed for one period. On the GaAs layer thus formed, a p-AlxGa1-xAs(x=0.9) layer and a p-GaAs layer doped by C, each having a thickness of1/4 times the oscillation wavelength in each medium, are repeated.Although the details are omitted in the drawing, the above-mentioned lowrefractive index layer is formed of stacking of a C-doped p-typeAlxGa1-xAs (x=0.9) layer having an optical thickness of λ/4–15 nm, aC-doped p-type AlAs selective oxidizing layer having an opticalthickness of 30 nm, and a C-doped p-type AlxGa1-xAs (x=0.9) of theoptical thickness of 2λ/4–15 nm.

The uppermost GaAs layer of the upper reflector 2206 is functions alsoas a contact layer 2207 that takes an electrical contact with anelectrode. In the case In content x of the well layer in the activelayer 2204 is 37% and the nitrogen content is 0.5% and the thickness ofthe well layer is 7 nm, the above-mentioned well layer accumulates acompressional strain (high distortion) of 2.5% with regard to the GaAssubstrate 2201.

The MOCVD growth apparatus used for the crystal growth of the GaInNAssurface-emission type laser diode of the present embodiment is asrepresented in FIG. 86.

For the source material of the GaInNAs active layer grown by the MOCVDprocess, TMG, TMI and AsH3 were used, and DMHy (dimethylhydrazine) wasused as the nitrogen source. Further, H₂ was uses as a carrier gas. DMHyis a material suited for low temperature growth like 600° C. or less,especially for growing a quantum well layer of large strain, whichrequires a low temperature growth process, in view of the lowdecomposition temperature. In the case that the distortion in the activelayer is large as in the case of the GaInNAs surface-emission type laserdiode of the present embodiment, the use of non-equilibrium lowtemperature growth process is preferable.

In the present embodiment, a GaInNAs layer is caused to grow at 540° C.In the present embodiment, the lower part reflector and the upper partreflector are grown by using the group III gas line A11 and the GaInNAsquantum well layer, the GaAs barrier layer, and the GaAs upper and lowerspacer layers are grown by using the group III gas line A12. At the timeof growing the GaInNAs layer, the group III gas line A11 is interruptedsuch that even a carrier is not supplied.

Thus, supply of the gas through the gas line in which the Al source hasbeen supplied is interrupted at the time of growth of the GaInNAs activelayer after the growth of the lower reflector, so as to avoidincorporation of at least the residual compound containing Al andremaining in the apparatus into the film with oxygen at the time ofgrowth of the active layer containing nitrogen. With this, it becamepossible to control admixing of oxygen into the active layer with Al.

In the present embodiment, the group III gas line A12 was used forgrowing the GaInNAs quantum well layer, GaAs barrier layer, and theupper and lower GaAs spacer layers. It is sufficient, however, toconduct the growth of at least the GaInNAs layer as the semiconductorlayer containing nitrogen by using the gas line A12. The group III gaslines A11 and A12 are formed separately up to the reaction chamber.However, they may be joined immediately before the reaction chamber intoa single line. It is preferable that the lines A11 and A12 are formedseparately throughout.

Further, after the stacked structure is formed as such, a mesa ofspecified size is formed so as to expose the sidewall of the p-AlAsselective oxidizing layer. Furthermore, by oxidizing of the exposedsidewall of AlAs with water vapor, an AlxOy current confinementstructure was formed. Further, planarization is achieved by burying theetched part with polyimide. Further, the polyimide film on the upperreflector is removed from the p-type contact part and also from the partwhere the optical window is formed, and a p-side electrode is formed onthe p-contact layer while avoiding the optical window. Further, ann-side electrode is formed on the rear side.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Because of the used of GaInNAs for the activelayer, it became possible to form a surface-emission type laser diode oflong wavelength band on the GaAs substrate. In order that the compoundcontaining Al and remaining in the apparatus being not incorporated intothe film with oxygen at the time of growth of the active layercontaining nitrogen, supply of the gas that has passed through the gasline in which the Al source material has been transported, is suppressedat the time of growth of the GaInNAs active layer. Thus, there is nochance that oxygen is incorporated into the active layer together withAk. With this, a GaInNAs surface-emission laser diode having a highoptical efficiency and oscillating at low threshold was produced with anMOCVD process suitable for mass production.

Further, because the current confinement was achieved by the selectiveoxidation of the selective oxidizing layer containing Al and As as theprincipal constituents, the laser diode of FIG. 87 can reduce thethreshold current significantly. According to the current-confinementstructure consisting of an Al oxide film selectively oxidized from aselective oxidizing layer, it becomes possible to form the currentconfinement layer closer to the active layer. As a result, spreading ofthe current is suppressed and the careers are confined efficiently intoa minute region not exposed to the atmosphere. Further, the refractiveindex is reduced as a result of formation of Al oxide film caused by theoxidation. Thus, the light can be confined efficiently to the minuteregion in which the careers are confined as a result of the convex lenseffect. Thereby, the efficiency is improved significantly and thethreshold current is reduced. Further, the production cost is reduced inview of the easiness of forming the current-confinement structure.

The semiconductor layers containing nitrogen and other group V elementssuch as GaInNAs have been mainly formed by an MBE process. However,because it is inherently a growth process conducted in a high vacuumenvironment, it is not possible to increase the supply rate of thesource material. Otherwise, there arises a problem that a large load isapplied to the exhaust system. More specifically, such an approachrequires a pump designed for a high vacuum evacuation system. Further,removal of the remaining materials and the like, from the MBE chambertends to increase the load of the evacuation system and the evacuationsystem easily fails. Because of this, only a poor throughput isobtained.

A surface-emission laser diode is constructed so as to sandwich anactive region containing at least one active layer, which produces thelaser light, by semiconductor multilayer reflectors. The thickness ofthe crystal growth layer of an edge surface emission laser diode isabout 3 μm. Contrary to this, a thickness exceeding 10 μm is needed in a1.3 μm wavelength band surface-emission laser diode. In an MBE process,it is not possible to increase the supply rate of the material in viewof the need of a high vacuum environment. The growth rate is about a 1μm/h. Thus, it is necessary for 10 hours at lowest to grow the thicknessof 10 μm, even in the case growth interruption is not made for changingthe source supply rate.

Usually, the thickness of the active region is very small (10% or less)as compared with the overall body of the laser diode, and most part isformed of the multilayer reflector. The semiconductor multilayerreflector is formed by alternately stacking a low refractive index layerand a high refractive index layer (20–40 pairs for example), each withthe optic film thickness of 1/4 times the oscillation wavelength in eachmedium (λ/4 thickness).

In the surface-emission laser diode on a GaAs substrate, the lowrefractive index layer (large Al content) and the high refractive indexlayer (small Al content) are formed by using an AlGaAs system materialand by changing the Al content. In fact, however, the resistance becomeslarge at the p-side because of the existence of the hetero barrier ateach of the layers. Thus, it is preferable to insert an intermediatelayer having an Al content intermediate between the low refractive indexlayer and the high refractive index layer, between the low refractiveindex layer and the high refractive index layer so as to reduce theresistance of the multilayer reflector.

Like this, the surface-emission laser diode is required to grow layersof as many as 100 layers of different compositions to form themultilayer reflector. In addition, it is necessary to provide theintermediate layer between the low refractive index layer and the highrefractive index layer of the multilayer reflector. Thus, it isnecessary to change the supply rate of the source materialsinstantaneously.

In an MBE process, the supply rate of the source is changed by changingthe temperature of source cell. Thus, it is not possible to control thesupply rate as desired. Therefore, it is difficult to reduce theresistance of the semiconductor multilayer reflector grown by the MBEprocess and the problem of high operational voltage cannot be avoided.

On the other hand, the MOCVD process can control the compositioninstantaneously by controlling the source gas flow rate. Further, itdoes not require a high vacuum environment as in the case of an MBEprocess. Further, a growth rate of 3 μm/h or more is easily achieved,and the throughput can be increased easily. Thus, the MOCVD process is agrowth method suitable for mass production.

Thus, according to the present embodiment, a surface-emission type laserdiode of the 1.3 μm band and low electric power consumption can berealized with low cost.

<Embodiment 21>

Next, an MOCVD apparatus according to Embodiment 21 of the presentinvention will be described.

FIG. 88 shows the construction of the reaction chamber 12 and the gasinlet port according to the present embodiment in detail. At the rightside of FIG. 88; there is shown the gas inlet port to the reactionchamber in a cross-sectional view.

The difference between the metal organic vapor phase growth apparatus ofthe present embodiment and the apparatus of FIG. 86 is that the groupIII source inlet port forming a part of the source gas inlet port to thereaction chamber 12 has a double pipe structure as enclosed with abroken line SC1 in FIG. 88.

When providing plural group III gas lines and provide plural source gasinlet ports in the reaction chamber 12 separately, there are unfavorablecases because of different film thickness distribution with each layers,depending on the position of the source gas inlet ports. By designing atleast the group III source gas introducing part of the source gasintroducing port to the reaction chamber in the form of double pipestructure like the present embodiment, the group III sources aresupplied from substantially the same point. Thereby, the difference ofdistribution of the film thickness for each layer is reduced as much aspossible. Further, the double pipe structure of the group III sourceinlet part forms actually a triple pipe structure as a whole as shown bya broken line S2 when the group V source material is taken intoconsideration.

By using the surface-emission laser diode of the present embodiment ofFIG. 87, it becomes possible to construct an opticaltransmission/reception module explained previously with FIG. 21 or theoptical transmission module explained with FIG. 22.

[Forty-Third Mode of Invention]

FIG. 89 shows the construction of a semiconductor device according to aforty-third mode of the present invention.

FIG. 89 is referred to. The semiconductor device of the present mode isformed on a substrate 2310. Thus, there is provided a lower surroundinglayer 2311 formed mainly of GatIn1-tPuAs1-u (0≦t≦1; 0≦u≦1), between thesubstrate 2310 and the active layer 2312 having a group III–V compoundsemiconductor layer containing nitrogen.

When the device of FIG. 89 is produced, an organic Al source isintroduced to the reaction chamber in the present mode during the growthof the above-mentioned lower surrounding layer 2311 or after the growththereof.

As for the substrate 2310, a compound semiconductor substrate such asGaAs, InP, GaP, and the like, is used. It is preferable to use a GaAssubstrate as the substrate 2310 so as to cause an epitaxial growth ofthe active layer (GaInNAs system active layer) 2312 having a group III–Vcompound semiconductor layer containing nitrogen and the surroundinglayer 2311 in excellent lamination.

GaNAs, GaInNAs, GaInAsSb, GaInNP, GaNP, GaNAsSb, GaInNAsSb, InAs,InNPAs, and the like, are listed as the material for the GaInNAs systemactive layer.

The above-mentioned surrounding layer 2311 functions so as to confinethe light, or confine the light and the careers, guide the light, ortransport the careers to the active layer, and the like. It should benoted that the lower surrounding layer 2311 is the layer between thesubstrate 2310 and the active layer 2312.

The above-mentioned lower surrounding layer 2311 is formed ofGatIn1-tPuAs1-u (0≦t≦1, 0≦u≦1). Because it does not contain Al, thislower surrounding layer 2311 does not easily cause edge surfacedestruction, and because of the large bandgap and small refractive indexas compared with the GaInNAs system active layer, the efficiency ofconfinement of the light and the careers is improved.

During the growth of the lower surrounding layer 2311 or before thegrowth thereof, an organic Al source material is introduced to thereaction chamber. The amount of the organic Al source material thusintroduced is preferably set such that the thickness of the filmcontaining Al and grown as a result of the introduction of the organicAl source material is 0.4 μm or less. This is because the degradation ofcrystal quality of the epitaxial growth film grown after introduction ofthe organic Al source material becomes conspicuous when the filmthickness becomes 0.4 μm or more. It should be noted that the lowersurrounding layer 2311 of the present invention includes a growth filmcontaining Al formed as a result of introduction of the organic Alsource to the reaction chamber. No other growth film containing Al isincluded.

FIG. 89 is referred to. It will be noted that the device has aconstruction of providing the lower surrounding layer 2311, formed ofone or more layers of GatIn1-tPuAs1-u (0≦t≦2, 1≦u≦) between thesubstrate 2310 and the GaInNAs system active layer 12. Further, an uppersurrounding layer (not shown) is provided on the active layer 2312. Itis also desirable that this upper part surroundings layer is formed ofIn1-tPuAs1-u (0≦t≦2, 0≦u≦), which does not easily cause damage of theedge surface. Further, other layers may be provided depending on thetype of the device.

By processing this stacked structure by a semiconductor processingtechnique such as a microfabrication process, a light-emitting device isformed. The light-emitting device may be a laser device, an LED device,and the like.

Thereby, it is possible to use a growth process such as MOCVD process,MOMBE process, CBE process, and the like.

Further, it is possible to use TMG, TEG, (CH₃)₂GaCl or Ga itself for theGa source material.

Further, it is possible to use (C₂H₅)₃In (TEI), InBr₃, or In itself forthe In source material.

It is possible to use PH₃, (CH₃)₃P, (C₂H₅)₃P, C₄H₉PH₂, or P itself forthe P source material.

It is possible to use AsH₃, (CH₃)₃As, (C₂H₅)₃As, C₄H₉AsH₂, or As itself,for the As source material.

Further, it is possible to use the amines of NH₂R, NHR₂, NR₃) (R is analkyl group or aryl group) in addition to hydrazines or NH₃ for thenitrogen source material. Here, hydrazines are defined as a substancesuch as hydrazine, monomethylhydrazine, dimethylhydrazine,buthylhydrazine, hydrazobenzene, and the like, that have the chemicalformula of NR₂NR₂ (R is hydrogen, alkyl group, or aryl group).

Examples of the organic Al source introduced during the growth of thelower surrounding layer includes TMA, TEA, (CH₃)₂AlCl, (CH₃)₂AlH, andthe like.

According to this mode, oxygen or water remaining in the reactionchamber or in the gas line is removed by causing a reaction with theorganic Al source material. Because of this, a high quality GaInNAssystem active layer containing little defects or impurities can beformed in the growth process conducted thereafter, even in the case anitrogen source material that tends to react with the residual oxygen orwater and incorporated into the film is used. As a result, it ispossible to obtain a semiconductor light-emitting device of highefficiency of optical emission, low threshold current, and longlifetime.

In the present mode, the lower surrounding layer 2311 includes at leastthe lower cladding 2412 and the lower optical guide layer 2413 as shownin FIG. 90. Further, introduction of an organic Al source material tothe reaction chamber is conducted before the growth or during the growthor after the growth of the lower part cladding layer 2412 and before thegrowth of the lower optical guide layer 2413.

It is preferable that the lower optical guide layer 2413 is formed ofGaAs.

FIG. 90 is referred to. There is formed a lower cladding layer 2412 thatconfines light and carriers in a part of the lower surrounding layer2311. Further, a lower optical guide layer 2413 is provided between thelower cladding layer 2412 and the active layer 2312 so as to guide thelight and improve the confinement of the light to the active layer.

Preferably, the introduction of the organic Al source material isachieved before the growth of the lower cladding layer 2412, or duringthe growth of the lower part cladding layer 2412, or before after thegrowth of the lower cladding layer 2412 but before the growth of thelower optical guide layer 2413. This is because oxygen taken into thefilm, which is caused to grow by introducing an organic Al sourcematerial, becomes a non-optical recombination center particularly whenthe film is grown on the optical guide layer in which a large amount ofcarriers of p-type and n-type exist simultaneously. Thereby, the lasercharacteristic is degraded. It is preferable to use GaInP for the lowercladding layer 2412 in view of the large bandgap and smaller refractiveindex.

In the case of this construction, it is preferable to use GaAs, whichgrows epitaxially on the GaAs substrate 2310, for the optical guidelayer 2413. It should be noted that GaAs has a bandgap and refractiveindex intermediate between the GaInNAs system active layer 2312 andGatIn1-tPuAs1-u (0≦t≦1, 0≦u≦1).

An organic Al source material is introduced to the reaction chamberduring the growth of the lower cladding layer 2412 or before or afterthe growth of the lower surrounding layer 2311. Because of this, oxygenis incorporated into the part near the cladding layer away from theactive layer 2312. However, the problem of non-optical recombinationcaused by oxygen does not take place even when a large amount ofcarriers of p-type and n-type are injected to the part neat the activelayer simultaneously. Thereby, production of a semiconductorlight-emitting device of high efficiency of optical emission, lowthreshold current, and long lifetime is guaranteed.

The GaAs optical guide layer 23 has the a bandgap and a refractive indexintermediate between the cladding layer 2412 and the GaInNAs systemactive layer. Further, the GaAs optical guide layer 23 is formed of thesame material as a substrate. Therefore, the GaAs optical guide layer 23can be grown on the GaAs substrate epitaxially. Thereby, a semiconductorlight-emitting device of higher efficiency of optical emission, lowthreshold current, and long lifetime is obtained.

According to such a process, various laser diodes such as the singlehetero junction type, double heterojunction type, separate-confinementheterojunction (SCH) type, multiple quantum well (MQW) structure type,can be produced. According to the type of the cavity, the laser diodesthus formed are classified into the Fabry-Perot(FP) type,distributed-feedback (DFB) type, distribution Bragg reflectors (DBR)type, and the like. According to the present mode, it becomes possibleto form an active layer of the GaInNAs system of high crystal qualitywith little defects or impurities. Thus, a long wavelength laser diodehaving a higher efficiency of optical emission, low threshold current,long lifetime and excellent temperature characteristics is obtained,wherein the laser diode uses the material of the GaInNAs system for theactive layer has an oscillation wavelength compatible with the quartzsystem optical fibers.

<Embodiment 22>

Next, an example of producing an SCH type edge surface emission laserdiode, having a GaInNAs system active layer by using an MOCVD apparatuswill be shown.

FIG. 91 is a diagram showing the example of the SCH-type edge-emissionlaser diode of the GaInNAs system according to the present invention.

As shown in FIG. 91, TMG, TMI, AsH₃, PH₃ and H₂Se are introduced intothe growth chamber at first, and an n-type GaInAsP cladding layer 2322is grown epitaxial on the n-type GaAs substrate 2321. Further, thegrowth of the cladding layer 2322 is interrupted once and a small amountof organic Al source material is introduced into the reaction chamberfor short period. Thereafter, the growth of the cladding layer 2322 isresumed.

In this case, it is also possible to introduce the organic Al sourcematerial while continuing the growth of the cladding layer 2322, withoutinterrupting the growth of the cladding layer 2322. Further, theintroduction of the organic Al source material may be conducted beforethe growth of the cladding layer or after the growth of the claddinglayer.

Further, it is preferable that the introduction of the organic Al sourcematerial is conducted during the growth of the cladding layer or beforethe growth of the cladding layer, although it is possible to introducethe organic Al source material during the growth of the guide layer.

It is preferable that the amount of the organic Al source materialintroduced by the introduction of the organic Al source material is setthat the film thickness of the growth film containing Al is 0.4 μm orless.

Next, by introducing TMG and AsH₃, the GaAs guide layer 2323 is grown.Next, by introducing TMG, TMA, TMI, AsH3 and DMHy, a GaInNAs activelayer 2324 is grown. Next, by introducing TMG and also AsH₃, a GaAsguide layer 25 is grown. Further, by introducing TMG, TMA, AsH₃, PH₃ andDMZn, a p-type GaInAsP cladding layer 2326 is grown. Furthermore, bystacking the p-type GaAs contact layer 27, an epitaxial layer structureconsisting of the lamination of p-type GaAs/p-typeGaInAsP/GaAs/GaInNAs/GaAs/n-type GaInAsP//n-type GaAs is formed.

After that, a p-type electrode part 2328 and an n-type electrode part2329 are provided, and a cavity is formed parallel to the film surfaceby a cleaving process. Thereby, an SCH type edge-emission laser diode isobtained.

By using the surface-emission laser diode of FIG. 91, it is possible toconstruct the optical transmission system shown in FIG. 36 or thewavelength multiplexing optical telecommunication system shown in FIG.37 can be formed easily.

<Embodiment 23>

FIG. 92 shows the construction of the MOCVD apparatus used in anEmbodiment 23. In FIG. 92, those parts explained previously aredesignated by the same reference numerals and the description thereofwill be omitted.

Also, it should be noted that FIG. 93 is a diagram showing an example ofthe edge-emission laser of the GaInNAs system produced by using theMOCVD apparatus of FIG. 93.

Hereinafter, explanation will be given with reference to FIGS. 92 and93.

FIG. 92 is referred to. The MOCVD apparatus has a heatable susceptor ina reaction chamber 2012 that is evacuated to a low pressure by thevacuum exhaust system C, and TMG, TMA, TMI, DMHy, AsH₃, PH₃, SeH₂ andZn(CH₃)₂ are supplied to the reaction chamber 2012 with the H₂ gas as acarrier gas. These gases are evacuated by the source gas evacuationsystem C including a rotary pump.

Next, an n-type GaAs substrate 2013 cleaned with an HCl aqueous solutionat the surface is held on the susceptor. Further, the pressure in thereaction chamber 2012 is reduced, and the susceptor is heated.Thereafter, TMG, TMI, PH₃ and SeH₂ are introduced into the reactionchamber 2013 and an n-type GaAs buffer layer 2362 is grown. Next, TMA isintroduced into the reaction chamber 2012 for 30 seconds with aflow-rate of 5 SCCM.

Thereafter, TMG, TMI, PH₃ and SeH₂ are introduced into the reactionchamber 2012 and an n-type GaInP lower cladding layer 2364 is grown.

By this process of introducing TMA, there is grown an oxygen-containingregion 2363 having a thickness of 50 nm and containing Al and oxygen, atthe interface between the n-type GaAs buffer layer 2362 and the n-typeGaInP lower cladding layer 2364.

Next, by introducing TMG and AsH₃ into the reaction chamber 2312, a GaAsguide layer 2365 is grown. Furthermore, by introducing TMG, TMI, AsH₃and DMHy, a GaInNAs active layer 2366 is grown. Next, by introducing TMGand AsH₃, a GaAs guide layer 2367 is grown. Next, by introducing TMG,TMI, PH₃ and DMZn, a p-type GaInP cladding layer 2368 is grown. Next, byintroducing TMG, AsH₃ and DMZn, a p-type GaAs contact layer 2369 isgrown. With this, an epitaxial layered structure of p-type GaAs/p-typeGaInP/GaInNAs SQW/n-type GaInP/n-type GaAs//n-type GaAs substrate,forming the laser structure is obtained.

After this, the SiO₂ insulation film is formed and the SiO₂ film isremoved to form a stripe form. Further, a p-type electrode film 2370 isdeposited by evaporation deposition process. Further, an n-typeelectrode film 2371 is formed on the rear surface of the substrate by anevaporation deposition process. Finally, a cavity is formed parallel tothe film surface by a cleavage process, and a broad stripe TQWedge-emission laser diode is produced. The threshold current density ofthe device thus produced was 0.9 kA/cm² in the continuous oscillationunder room temperature.

As a comparison, a broad stripe TQW edge-emission laser diode of thesame construction was produced continuously, without introducing TMAbetween the growth of the buffer layer 2362 and the growth of thecladding layer 2364. In this case, the threshold current density was 1.3kA/cm² in the case of the continuous oscillation under room temperature.

Thus, there occurs a decrease of threshold current density in the eventTMA is introduced immediately before the growth of the cladding layer.It is thought that this has been caused because oxygen and waterremaining in the reaction chamber or gas line is removed by theintroduction of TMA. Thus, a high quality GaInNAs active layercontaining little impurities or defects is formed even if DMHy, whicheasily causes incorporation of oxygen into the film, is used with theprocess of forming the active layer conducted after the process ofintroducing TMA.

<Embodiment 24>

In the present invention, the MOCVD apparatus of FIG. 92 is used. Anepitaxial layered body of laser structure of p-type GaAs/p-typeGaInP/GaAs/GaInNAs DQW/GaAs/n-type GaInP//n-type GaAs substrate isformed under the condition identical with the embodiment 23, except thatTMA is introduced for a short period during the growth of the lowercladding layer 2364.

FIG. 94 shows an example of the GaInNAs system edge-emission laser diodeproduced by using the MOCVD apparatus of FIG. 92 in the presentinvention.

Hereinafter, the film formation process will be explained with referenceto FIG. 92 and FIG. 94.

First, an n-type GaAs substrate 2381 having a surface cleaned with anHCl aqueous solution is held on a susceptor. Next, the pressure in thereaction chamber 2352 is reduced and the susceptor is heated.Thereafter, TMG, AsH₃ and SeH₂ are introduced into the reaction chamberand an n-type GaAs buffer layer 2382 is grown. Next, by introducing TMG,TMI, PH₃ and SeH₂ into the reaction chamber 2852, an n-type GaInP lowercladding layer 2383 is grown. During the growth of this GaInP lowercladding layer 2383, TMA is introduced into the reaction chamber 12 for30 seconds with a flow-rate of 5 SCCM, without interrupting the growth.Thereafter, the growth of the n-type GaInP lower cladding layer 2383 isresumed. With this process, an Al-containing layer 2384 containing Aland oxygen is formed in the midway of growth of the n-type GaInP lowercladding layer with a thickness 120 nm.

Next, TMG and AsH₃ are introduced and a GaAs optical guide layer 2385 isgrown. Next, TMG, TMI, AsH₃ and DMHy are introduced and a GaInNAs activelayer 2386 is grown together with a barrier layer of GaAs. Next, byintroducing TMG and AsH₃, a GaAs optical guide layer 2387 is grown.Next, by introducing TMG, AsH₃ and DMZn, a p-type GaInP upper claddinglayer 2388 is grown. Further, by introducing TMG, AsH₃ and DMHy, ap-type GaAs contact layer 2389 is grown. With this, an epitaxial layeredbody of the laser structure of p-type GaAs/p-type GaInP/GaAs/GaInNAsDQW/GaAs/n-type GaInP//n-type GaAs substrate is formed.

After this, an SiO₂ insulation film is formed and patterned this into astripe form. Further, a p-type electrode film 2390 is deposited by anevaporation-deposition process. Next, an n-type electrode film 2391 isdeposited on the rear side of the substrate by an evaporation depositionprocess. Finally, a cavity is formed parallel to the film surface by acleavage process, and a broad stripe DQW edge-emission type diode laseris obtained. It was confirmed that the threshold current density of thisdevice is 0.6 kA/cm² in the case of continuous oscillation under roomtemperature.

FIG. 95 shows the results of SIMS analysis of the layered body producedunder the same condition. Thus, FIG. 95 shows the depth profile ofnitrogen and oxygen in the vicinity of the active layer.

FIG. 95 is referred to. It will be noted that there is no peak of oxygenobserved in the vicinity of the active layer 2386 vicinity, and theeffect of introduction of TMA was confirmed.

For the purpose of comparison, a broad stripe DQW edge-emission laserdiode of the same construction was formed under the same condition, butcontinuously without introducing TMA during the growth of the claddinglayer. In this case, it was confirmed that the threshold current densityis 0.9 kA/cm² in the continuous oscillation under room temperature. Itshould be noted that the laser diode used with this comparative test hasbeen produced with the same condition as the sample used in the surveyexperiment and has the same construction.

Thus, in the case TMA is introduced during the growth of the claddinglayer, there occurs degradation of the threshold current density. Thisis because oxygen and water remaining in the reaction chamber and thegas line are removed by introducing TMA. Thus, it becomes possible toform the GaInNAs active layer free from oxygen capturing, even if DMHy,which easily cause incorporation of oxygen into the film, is used in theprocess of growing the active layer.

[Forty-Fourth Mode of Invention]

In the present mode, the present invention provides a fabricationprocess of a semiconductor light-emitting device having a semiconductorlayer containing Al between the substrate and the active layercontaining nitrogen, wherein the semiconductor layer containing Al andthe active layer containing nitrogen are grown respectively by using ametal organic source of Al and a nitrogen compound source, and whereinthere is provided a process of removing the residual Al source, Alreactant, Al compound or Al remaining in the growth chamber by anetching gas, after the end of growth of the semiconductor layercontaining Al but before the start of growth of the active layercontaining nitrogen. As explained before, the residual Al species causethe incorporation of oxygen, which in turn becomes the cause ofnon-optical recombination, into the active layer in the production of asemiconductor light-emitting device that has an active layer of a groupIII–V semiconductor material containing nitrogen on a group III–Vcompound semiconductor layer containing Al. Because of this, in thepresent mode of the invention, a gas that reacts with the residual Alspecies remaining on the reaction chamber wall, the heating body, thejig, and the like, holding the substrate, and the like, is supplied tothe reaction chamber after the growth of the semiconductor layercontaining Al but before the growth of the active layer containingnitrogen. Thereby, the incorporation of oxygen into the active layer issuppressed by removing the residual Al species by such a gas.

By this approach, it is possible to reduce the Al concentration in theactive layer containing nitrogen to 1×10¹⁹ cm⁻³ or less, and continuousoscillation became possible at room temperature. Further, by reducingthe Al concentration in the active layer containing nitrogen to be2×10¹⁸ cm⁻³ or less, it becomes possible to achieve an optical emissioncharacteristics equivalent to the case in which the active layer isformed on a semiconductor layer not containing Al. Reference of Table 4before should be made.

In order to remove the residual Al species such as the Al sourcematerial, Al reactants, Al compound, or Al remaining in the growthchamber by an etching gas, it is effective to supply an organic nitrogencompound gas into a growth chamber as an etching gas.

As an example of the gas that reacts with such Al-containing residue andcan be used for the removal thereof, an organic compound gas may beused. It is clear that DMHy, which is an organic compound gas, reactswith Al-containing residue when it is supplied from a DMHy cylinder atthe time of growth of the active layer containing nitrogen.

Therefore, when an organic compound gas is supplied from an organiccompound gas cylinder before the growth of the active layer containingnitrogen but after the growth of the semiconductor layer containing Al,it becomes possible to remove the Al-containing residues remaining onthe reaction chamber sidewall, heating body, or on the jigs that holdthe substrate, by causing a reaction therewith. Thus, incorporation ofoxygen into the active layer is suppressed. By using the same gas usedfor the nitrogen source material for growing the active layer containingnitrogen, there is no need of providing a separate gas line.

Further, in the process of removing the residual Al species such as theAl source material, Al reactants, Al compound, or Al from the growthchamber by an etching gas, it is as well possible to supply a gascontaining oxygen into the growth chamber as the etching gas.

O₂, H₂O, and the like, are examples of the gas useful for removing theAl-containing residue by causing a reaction. As noted above, it has beenfound that oxygen is incorporated into the active layer at the time ofgrowing the active layer containing nitrogen together with Al. Thus, agas containing oxygen such as O₂, H₂O, and the like, reacts with theAl-containing residue.

Therefore, when a gas containing oxygen such as O₂ or H₂O is suppliedbefore the growth of the active layer containing nitrogen but after thegrowth of the semiconductor layer containing Al, it becomes possible toremove the Al-containing residue remaining on the reaction chambersidewall, heating body, or on the jig that holds the substrate bycausing a reaction therewith. Thus, it is possible to suppress theincorporation of oxygen into the active layer.

As will be understood from the SIMS profile of FIG. 8 explainedpreviously, a large amount of Al is taken into the first layer of theactive layer containing nitrogen. On the other hand, there is little Alincorporation in the second layer. Thus, it will be understood that itis possible to remove Al-containing residue by merely supplying a gascontaining only a very small amount of oxygen. Of course, it isnecessary that the excessive oxygen-containing gas is removed before thegrowth of the active layer. Thus, it is preferable to avoid excessivesupply of the oxygen-containing gas. Otherwise, the removal of the gascontaining the oxygen becomes difficult.

Furthermore it is preferable to grow a GaxIn1-xPyAs (0<x≦1, 0<y≦1)layer, in the semiconductor light-emitting device that was manufacturedwith the foregoing method, between the semiconductor region from whichremoval of the residual Al species such as the Al source material, Alreactants, Al compounds, or Al remaining in the growth chamber has beenmade by the etching gas, and the active layer containing nitrogen.

For example, the removal of the residual Al species such as the Alsource material, Al reactants, Al compound, or Al remaining in thegrowth chamber with the etching gas, may be conducted by interruptingthe growth process. In this case, however, there is a possibility thatthere may be caused defects on the epitaxial substrate surface due tothe damage caused by the etching gas, and the like. Thus, when such aninterface is the formed in the active region in which injection ofcarriers is made, there are formed non-optical recombination centers,and the efficiency of optical emission of the light-emitting device isdegraded.

Thus, injection of the carriers to such a growth interruption interface,formed by the etching gas, is almost eliminated when a GaxIn1-xPyAs(0<x≦1, 0<y≦1) layer having a bandgap energy larger than the bandgapenergy of the material forming the growth interruption surface is grownbetween the growth interruption interface and the active layercontaining nitrogen. Thereby, degradation of efficiency of opticalemission disappears. If a SIMS analysis is applied to such a growthinterruption interface, oxygen or nitrogen or Al would be detected.

Thus, in the semiconductor light-emitting device having thesemiconductor layer containing Al between the substrate and the activelayer containing nitrogen, the semiconductor layer containing Al and theactive layer containing nitrogen are grown respectively by using anorganic-metal Al source and a nitrogen compound source material.Further, there is a feature in that a GaNAs layer or a GaInNAs layer isformed between the semiconductor layer containing Al and the activelayer containing nitrogen.

Furthermore, it is possible to conduct the process of removing theresidual Al species of the Al source material, Al reactant, Alcompounds, or Al remaining in the growth chamber, by using the etchinggas while simultaneously conducting a crystal growth when forming such astructure. For instance, a GaNAs layer or a GaInNAs layer is grown inthe form incorporating Al and oxygen when GaAs, which does not containnitrogen or Al, is provided as an intermediate layer between thesemiconductor layer containing Al and the active layer containingnitrogen and the DMHy gas acting as an etching gas is supplied duringstep of growing the GaAs layer or the GaInAs layer.

With this, the residual Al species such as the Al source material, Alreactant, Al compound, or Al remaining in the growth chamber areremoved. The incorporation of oxygen to the active layer is suppressed.In this case, the GaNAs layer or the GaInNAs layer has to be set thecondition so that they have a larger bandgap than the bandgap of theactive layer. For example, by setting up the DMHy vapor phase ratio:[DMHy]/([DMHy]+[AsH₃]) to be small and by setting up the growthtemperature highly, and further by setting up the In composition large,incorporation of nitrogen is reduced.

In the semiconductor light-emitting device of this mode, any of GaAs,GaInAs, GaAsP, GaInPAs, and GaInP layers may be formed between the GaNAslayer and the active layer containing nitrogen.

In this case, the process of removing the residual Al species such asthe Al source material, Al reactants, Al compound, or Al remaining inthe growth chamber causes incorporation of Al and oxygen into the GaNAslayer or the GaInNAs layer. Thus, oxygen becomes a non-opticalrecombination center when there is a GaNAs layer or GaInNAs layer in theactive region in which injection of carriers takes place, and theefficiency of optical emission at the time light-emission operation.

When any of GaAs, GaInAs, GaAsP, GaInPAs or GaInP layer having a bandgapenergy larger than the GaNAs layer or GaInNAs layer and not containingAl is formed between the active layer containing nitrogen and the GaNAslayer or GaInNAs layer, the injection of carriers into the GaNAs layeror GaInNAs layer is almost eliminated. Thereby, falling of efficiency ofoptical emission is eliminated.

In the present mode, it should be noted that the semiconductorlight-emitting device is a semiconductor light-emitting device providedwith a semiconductor layer containing Al between the substrate and theactive layer containing nitrogen. The semiconductor layer containing Aland the active layer containing nitrogen are grown by using a metalorganic Al source and a nitrogen compound source material, respectively.Further, there is a feature in that a GaInNP layer or GaInNPAs layer isformed between the semiconductor layer containing Al and the activelayer containing nitrogen.

The process of removing the Al source material, or Al reactant, or Alcompound, or Al remaining in the growth chamber with the etching gasmaybe conducted while conducting a crystal growth process. For instance,the GaInNP layer or the GaInNPAs layer are grown in the form ofincorporating Al and oxygen when the DMHy gas is supplied as an etchinggas during the growth process of the intermediate layer, in the casethat the GaInP layer or GaInPAs layer not containing nitrogen and Al isprovided between the semiconductor layer containing Al and the activelayer containing nitrogen as the intermediate layer.

With this, the Al source material or Al reactant, or Al compound, or Alremaining in the growth chamber is removed. Thereby, incorporation ofoxygen into the active layer can be suppressed. In this case, it isnecessary to set the condition such that a bandgap larger than thebandgap of the active layer is realized. For example, incorporation ofnitrogen is reduced by reducing the DMHy vapor phase ratio:[DMHy]/([DMHy]+[AsH₃]+[PH₃]) and by increasing the growth temperature.

Thereby, it is preferable that a layer of GaAsP, GaInPAs or GaInP oflarge bandgap energy larger than the GaInNP layer or GaInNPAs layer isformed between the GaInNP layer or the GaInNPAs layer and the activelayer containing nitrogen.

The process of removing the residual Al species such as the Al sourcematerial, Al reactants, Al compound, or Al remaining in the growthchamber like this is a process of growing the GaInNP layer or theGaInNPAs layer, and Al and oxygen are incorporated into the film. Thus,oxygen becomes a non-optical recombination center when the GaInNP layeror the GaInNPAs layer exists in the active region in which injection ofcarriers takes place, and the efficiency of optical emission at the timeof operation of the light-emitting device is degraded.

When there is formed any of the GaAsP, GaInPAs or GaInP layer having abandgap energy larger than the GaInNP layer or the GaInNPAs layer andnot containing Al and nitrogen is provided between, the GaInNP layer orthe GaInNPAs layer and the active layer containing nitrogen, injectionof carriers into the GaInNP layer or the GaInNPAs layer is almosteliminated. Thereby, the efficiency of optical emission is not degraded.

A surface-emission laser diode device can be formed by using such asemiconductor light-emitting device.

For the semiconductor layer containing nitrogen, GaNAs, GaInNAs, InNAs,GaAsNSb, GaInNAsSb, and the like are listed. Hereinafter, the example ofGaInNAs will be explained.

By adding N to GaInNAs having a lattice constant larger than GaAs, itbecomes possible to achieve a lattice matching to GaAs, and the bandgapis reduced. As a result, optical emission in the 1.3 μm or 1.55 μm bandbecome possible. Further, because it is a GaAs substratelattice-matching system, it is possible to use AlGaAs or GaInP ofwidegap material for the cladding layer.

Furthermore, the bandgap becomes small as noted above by the addition ofN. Thereby, the energy level of the conduction band and valence band isreduced. As a result, the band discontinuity of the conduction bandbecomes very large at the heterojunction, and it is possible to reducethe temperature dependence of the operating current of the laser.

Further, the surface-emission type laser diode is advantageous in theparallel transmission in view of small size, low electric powerconsumption and further in view of the possibility of two-dimensionalintegration. It has been difficult to obtain a practical performance fora surface-emission type laser diode when the GaInPAs/InP system is used.However, when the GaInNAs material system is used, it becomes possibleto use the Al(Ga)As/(Al)GaAs semiconductor multilayer film distributedBragg reflector or the current-confinement structure formed by theselective oxidation of AlAs, which have been successfully used with the0.85 μm band surface-emission type laser diode and the like, that uses aGaAs substrate. Thus, the device is realized easily.

In order to achieve this, improvement of crystal quality of the GaInNAsactive layer, decrease of resistance of the multilayer reflector, andimprovement of the crystal quality and controllability of the multilayerfilm structure forming the surface-emission type laser diode, have beenimportant. According to, a/the present invention, a surface-emissiontype laser diode of low resistance and low drive voltage, highefficiency of optical emission, low threshold current and excellenttemperature characteristics is realized easily with low cost.

Particularly, in the surface-emission type laser diode produced withsuch a method, there is provided a GaxIn1-xPyAs (0<x≦1, 0<y≦1) layerbetween the semiconductor region from which removal of the Al sourcematerial, or Al reactant, or Al compound, or Al remaining in the abovegrowth chamber has been conducted by an etching gas and the active layercontaining nitrogen. It is desirable to conduct the removing processthat uses the etching gas in correspondence to the semiconductordistribution Bragg reflector.

There is a possibility that the non-optical recombination may be causedby oxidation and the like, when the removal process is conducted duringthe active region, in which injection of carriers takes place. Thereby,the efficiency of optical emission is degraded. In the case of thestructure as in claim 10 in which a GaxIn1-xPyAs (0<x≦1, 0<y≦1) layer isgrown as a part of the reflector after the removal of the residual Alspecies such as the Al source material, Al reactant, Al compound or Alremaining in the growth chamber but before the growth of the activelayer, it becomes possible to form an active region in the region closerto the active layer as compared with the GaxIn1-xPyAs (0<x≦1, 0<y≦1)with a narrow gap material (such as GaAs). In this case, there is noconcern about degradation of efficiency optical emission. Thus, itbecomes possible to eliminate the effect of the non-opticalrecombination centers in the region from which removal of theAl-containing residual material has been conducted on the deviceperformance. Thereby, it becomes possible to obtain a surface-emissionlaser diode operating at low threshold current with excellenttemperature characteristics. It should be noted that the etching processmay be conducted in the cavity region. Further, it is preferable toprovide a widegap material between the region conducted with the removalprocess and the active layer. See fiftieth mode to be explained later.

Further, it is possible to realize a low-cost optical transmissionmodule or optical transmission/reception module not requiring a coolingdevice by using such a surface-emission laser diode. Further, it ispossible to realize an optical telecommunication system such as a lowcost optical fiber telecommunication system or optical interconnectionsystem by using such a surface-emission laser diode.

<Embodiment 25>

Next, description will be made on a GaInNAs surface-emission laser diodeaccording to Embodiment 24 of the present invention.

FIG. 96 is a diagram showing the structure of the GaInNAssurface-emission type laser diode according to Embodiment 24. It shouldbe noted that the structure of FIG. 96 resembles the structure explainedwith reference to FIG. 17 previously explanation thereof will be omittedby providing the same reference numerals to those parts explainedpreviously.

As shown in FIG. 96, the surface-emission type laser diode of thepresent embodiment includes an n-semiconductor distributed Braggreflector 141 provided on a (100)-oriented n-type GaAs substrate 140having a size of 2 inches, wherein the distributed Bragg reflector 141consists of a periodical structure in which an n-type AlxGa1-xAs (x=0.9)layer and an n-GaAs layer are repeated alternately for 35 times, eachwith an optical film thickness of 1/4 times the oscillation wavelengthin each medium. Further, an undoped lower GaAs spacer layer 142 isformed thereon, and a multiple quantum well active layer 143 containingthree GaxIn1-xNyAs1-y (x, y) well layers and corresponding GaAs barrierlayers is formed on the spacer layer 142, and an undoped upper GaAsspacer layer 144 is formed further on the multiple quantum well activelayer 143.

Further, a p-type semiconductor distributed Bragg reflector 145 isformed thereon. The upper reflector 145 includes a low refractive indexlayer having an optical film thickness of 3λ/4, in which an AlAs layer145 ₁ used for the selective oxidizing layer is sandwiched with a pairof AlGaAs layers, and a GaAs layer having an optical film thickness ofλ/4 is formed with one period. Further, a periodical structure of 25periods, for example, is formed thereby by alternately laminating aC-doped p-type AlxGa1-xAs (x=0.9) and a p-type GaAs layer with anoptical film thickness of 1/4λ. Further, the low refractive index layerof the optical film thickness of 3λ/4 is composed of a C-doped p-typeAlxGa1-xAs (x=0.9) layer having an optical film thickness of λ/4–15 nm,a C-doped p-type AlAs selective oxidizing layer having an optical filmthickness of 30 nm, and a C-doped p-type AlxGa1-xAs (x=0.9) layer havingan optical thickness of 2λ/4–15 nm.

The GaAs layer at the uppermost part of the upper part reflector 145functions also as a contact layer 145 ₂ for making a contact with theelectrode. Here, it should be noted that the In content x of the welllayer in the active layer is 37% and contains nitrogen with 0.5%. Thethickness of the well layer is set to be 7 nm. The well layer thusformed accumulates therein a compressional strain of about 2.5% (highdistortion) with regard to the GaAs substrate 140.

For the source material of the GaInNAs active layer grown by an MOCVDprocess, TMG, TMI, AsH3 were used for the source material of the groupIII element and DMHy (dimethylhydrazine) was used for the sourcematerial of nitrogen. Further, H₂ was used for the carrier gas. DMHy,decomposing at a low temperature, is a source material especially suitedfor a low temperature growth process conducted at 600° C. or less, andis a desirable source material for growing a quantum well layer of largestrain, in which a low temperature growth process is required. In thecase the strain is large as in the case of the active layer of theGaInNAs surface-emission type laser diode of the present embodiment, alow temperature growth process which realizes a non-equilibrium process,is desirable. In the present embodiment, the GaInNAs layer is caused togrow at 540° C.

In the present embodiment, the growth of the lower GaAs spacer layer 142is interrupted halfway for suppressing the incorporation of oxygen tothe active layer and for avoiding decrease of efficiency of opticalemission, and the Al-containing residue was eliminated by using the DMHygas. When DMHy is supplied by using the DMHy cylinder, the Al-containingresidue remaining to on the reaction chamber sidewall, heating body oron the jig holds the substrate are removed by causing a reaction, andthe incorporation of oxygen into the active layer can be suppressed.

This process may be conducted after the growth of the semiconductorlayer containing Al but before the growth of the active layer.

Further, a mesa of specified size is formed so as to expose at least thesidewall of the p-AlAs selective oxidizing layer 145 ₁. The AlAs layer145 ₁ having the sidewall thus exposed was oxidized from the sidewallwith water vapor. Thereby, an AlxOy current-confinement structure 146 isformed. Next the etched part was filled with the polyimide 210 forplanarization. Further, the polyimide film on the reflector 145 wasremoved from the p-contact part and from the optical window. Further, ap-side electrode 149 was formed on the p-type contact layer 145 ₂excluding the optical window, and an n-side electrode 150 was formed onthe rear side.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Thus, by using GaInNAs for the active layer,it became possible to construct a surface-emission type laser diode oflong wavelength band on a GaAs substrate. Also, the compound containingAl and remaining in the apparatus is eliminated by using the etchinggas, such that the compound containing Al is not incorporated into thefilm at the time of growth of the active layer containing nitrogen withoxygen. Thus, it is possible to eliminate admixing of oxygen into theactive layer together with Al. With this, it has become possible toproduce a GaInNAs surface-emission type laser diode having highefficiency of optical emission and oscillating at low threshold with anMOCVD process, which is advantageous for mass production.

Further, in view of providing current confinement by a selectiveoxidation of a selective oxidizing layer containing Al and As as aprincipal component, it became possible to reduce the threshold current.According to the current-confinement structure that uses the currentconfinement layer consisting of an Al oxide film formed by selectiveoxidation of the selective oxidizing layer, it becomes possible to formthe current confinement layer close to the active layer and spreading ofthe carriers is suppressed and the carriers are confined efficientlyinto a minute region not exposed to the atmosphere. Further, the lightcan be confined into the minute region by the convex lens effect in viewof the fact that the refractive index is reduced as a result of theoxidation process that forms the Al oxide. As a result, it becomespossible to confine the light into the minute region in which thecarriers are carriers also confined, with high efficiency. Thereby, theefficiency is improved remarkably. And the threshold electric current isreduced. Further, the production cost is reduced in view of easiness offormation of the current-confinement structure.

As for growth of the semiconductor layer containing nitrogen and othergroup V element such as GaInNAs, MBE process has been used mainly. It isinherently a growth process in a high vacuum environment. Therefore, thesupply rate of the source material cannot be increased. As explainedpreviously, increase of the source supply rate increases the load of theevacuation system in an MBE process. Also, an evacuation pump definedfor a high-vacuum evacuation system is necessary in the MBE process. Forthe removal of the residual source material and the like, inside the MBEchamber, a large load is applied to the evacuation system, and theevacuation system easily undergoes failure. Thereby, frequentmaintenance is necessary and it is not achieve a high throughput.

It should be noted that a surface-emission type laser diode has aconstruction in which an active region including at least one activelayer that produces a laser beam is sandwiched by semiconductormultilayer reflectors. An edge-emission laser diode has a thickness ofabout 3 μm for the crystal growth layers. On the other hand0 in the caseof a 1.3 μm wavelength band surface-emission type laser diode, thethickness exceeding 10 μm becomes necessary. In the MBE process, a highvacuum environment is needed. Thus, it is not possible to increase thesource supply rate. The growth rate is about 1 μm/h, and at least 10hours are needed for growing the thickness of 10 μm, provided thatinterruption of growth, needed for changing the source supply rate, isnot counted for.

However, the thickness of the active region is usually very small ascompared with the whole body (10% or less), and most part forms themultilayer reflector. The semiconductor multilayer reflector is formedby laminating a low refractive index layer and a high refractive indexlayer alternately with the optical thickness of 1/4 times theoscillation wavelength (λ/4 thickness) in each medium (20˜40 times, forexample).

In the surface-emission type laser diode formed on a GaAs substrate, theAlGaAs system material is used and the Al content is changed between thelow refractive index layer (high Al content) and a high refractive indexlayer (low Al content). In fact, however, the resistance becomes largeespecially in the p-side because of the existence of the heterobarrierat each layer. Therefore, it is preferable to insert an intermediatelayer having an Al content between the low refractive index layer andthe high refractive index layer so as to reduce the resistance of themultilayer reflector.

Like this, it is necessary to grow semiconductor layers of differentcompositions over 100 layers in the case of a surface-emission typelaser diode. In addition, there are provided the intermediate layersbetween the low refractive index layers and the high refractive indexlayers in the case of a multilayer reflector. Thus, there is a need tocontrol the source supply rate instantaneously. However, in the MBEprocess, the source supply rate is changed by changing the temperatureof the source cell, and it is not possible to control the composition asdesired. Thus, it is difficult to reduce the resistance in thesemiconductor multilayer reflector grown by an MBE process, and it isfurther difficult to form the intermediate layer. Thus, it is inevitablethat the operating voltage is increased.

On the other hand, in the case of an MOCVD process, it is sufficient tocontrol the source gas flow rate and the composition can be controlledinstantaneously. Thereby, it does not require the high vacuumenvironment as in the case of the MBE process. Further, the growth rateis increased to 3 μm/h or more, for example. Thereby, a high throughputis easily achieved. Thus, it is a growth process well suitable for massproduction.

Thus, according to the present invention, it is possible to realize asurface-emission type laser diode of the 1.3 μm band at low cost and lowelectric power consumption.

<Embodiment 26>

Next, a GaInNAs surface-emission type laser diode according toEmbodiment 26 of the present invention will be described.

The GaInNAs surface-emission type laser diode of the present embodiment26 has the same construction as the laser diode of Embodiment 25 of FIG.96.

The only difference with regard to the previous embodiment is that thegrowth is interrupted halfway of the growth of the GaAs lower spacerlayer 142 and oxygen is supplied so as to remove the Al source material,or Al reactant, or Al compound, or Al remaining in the growth chamber.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Because GaInNAs is used for the active layer,it became possible to form a surface-emission type laser diode of longwavelength band on a GaAs substrate.

In order to avoid incorporation of the compound containing Al remainingin the apparatus during the growth of the active layer containingnitrogen together with oxygen, the growth is interrupted between thelayer containing Al and the active layer containing oxygen, and oxygenis supplied as an etching gas. Thus, Al was incorporated into the growthinterruption interface together with oxygen. On the other hand, thecompound containing Al remaining in the reaction chamber, in otherwords, the residual Al species containing Al were excluded before thegrowth of the active layer. Thereby, admixing of oxygen into the activelayer together with Al was suppressed. With this, it was possible toproduce a GaInNAs surface-emission type laser diode having a highefficiency of optical emission and oscillating with a low threshold wasproduced by an MOCVD process, which is suitable for mass production.

<Embodiment 27>

Next, explanation will be made about a GaInNAs surface-emission typelaser diode according to Embodiment 27 of the present invention.

The laser diode of the present embodiment has a construction of FIG. 97.In FIG. 97, those parts explained previously are designated by the samereference numerals and the description thereof will be omitted.

The present embodiment differs from the embodiment of FIG. 96 in thatthe process of removing the residual Al species of the Al sourcematerial, Al reactants, Al compound, or Al remaining in the growthchamber is conducted by supplying DMHy during the growth of the GaAslower spacer layer 203 to grow a GaInNAs layer 160. This GaInNAs layer160 has a composition such that the bandgap energy is larger as comparedwith the GaInNAs active layer 143.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Further, it became possible to form asurface-emission type semiconductor laser element of long wavelengthband on a GaAs substrate as a result of use of GaInNAs for the activelayer. There, DMHy is supplied as an etching gas, so that the compoundcontaining Al and remaining in the apparatus is not incorporatedtogether with oxygen during the growth of the film at the time of growthof the active layer containing nitrogen. Thereby, the GaInNAs layer 160it grown. Thus, Al is taken into the GaInNAs layer in which the removalprocess has been conducted together with oxygen. On the other hand, thecompound containing Al and remaining in the reaction chamber iseliminated before the growth of the active layer. Thus, admixing ofoxygen into the active layer together with Al is suppressed. The GaInNAslayer 160 used for this removal process can be regarded as a dummy layerof the active layer. With this, a GaInNAs surface-emission type laserdiode having a high efficiency of optical emission and oscillating witha low threshold is produced by an MOCVD process, which is suitable formass production.

<Embodiment 28>

Next, explanation will be made on a GaInNAs surface-emission type laserdiode according to Embodiment 28.

FIG. 28 shows the structure of a GaInNAS surface-emission typesemiconductor laser element according to Embodiment 28.

The process of the present embodiment differs from the process ofembodiment 25 in the point that removal of the residual Al species suchas the Al source material, Al reactant, Al compound, or Al remaining inthe growth chamber is conducted out in the lower reflector region 141.The low refractive index layer constituting the lower reflector isformed almost of AlGaAs. Further, the single laser closest to the activelayer is formed of the GaxIn1-xPyAs (x=0.5, y=1) layer 161. There,interruption of the growth is conducted during the growth of the GaAslayer, which is a high refractive index layer and located underneath thelayer 161. During the growth interruption, DMHy is supplied.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Thus, a surface-emission type semiconductorlaser device of long wavelength band was formed on a GaAs substrate 140as a result of use of GaInNAs for the active layer 143.

Here, DMHy was supplied as an etching gas between the semiconductorlayer containing Al and the active layer containing nitrogen so that thecompound containing Al and remaining in the apparatus is not taken intothe active layer containing nitrogen, together with oxygen. Thus, thecompound containing Al and remaining in the reaction chamber waseliminated before the growth of the active layer. Thereby, admixing ofoxygen into the active layer together with Al was suppressed. On theother hand, such an interface is subjected to damages by the etching gasand the like, and there is a possibility of formation of defects.Further, there is a possibility that nitrogen, oxygen or Al isincorporated and there is formed a non-optical recombination center.

In the present embodiment, on the other hand, a GaInPAs layer 161 havinga wide bandgap is interposed between the growth interruption interfaceand the GaInNAs active layer. Thus, injection of carriers into thegrowth interruption interface is suppressed. Thereby, the degradation ofefficiency of optical emission, caused by the non-optical recombinationcenter, is prevented.

With this, it became possible to produce a GaInNAs surface-emission typesemiconductor laser element having a high efficiency of optical emissionand oscillating at low threshold with an MOCVD process suitable for massproduction.

<Embodiment 29>

Next, explanation will be made on a GaInNAs surface-emission type laserdiode according to Embodiment 29 of the present invention.

FIG. 99 is a diagram showing the structure of a GaInNAs surface-emissiontype semiconductor laser element of Embodiment 29. In the drawings,those parts corresponding to the parts explained previously aredesignated by the same reference numerals and explanation thereof willbe omitted.

The difference of the present embodiment over Embodiment 28 is that theremoval of the residual Al species such as the Al source material, Alreactant, Al compound, or Al remaining in the growth chamber isconducted during the growth of the GaxIn1-xPyAs (x=0.5, y=1) layer thatconstitutes a low refractive index layer of the lower reflector.Further, DMHy is supplied halfway of the growth of the GaInP layer 161to grow a GaInNP layer 162.

The oscillation wavelength of the surface-emission type laser diode thusproduced was about 1.3 μm. Because of used of GaInNAs for the activelayer, it became possible to grow the surface-emission typesemiconductor laser element of long wavelength band on a GaAs substrate.In the present embodiment, DMHy is supplied as an etching gas, and aGaInNP layer 162 was grown such that the compound containing Al, inother words, the residual Al species remaining in the apparatus are notincorporated into the film together with oxygen at the time of growth ofthe active layer containing nitrogen. Therefore, Al was incorporatedinto the GaInNP layer 162 together with oxygen. Thus, the compoundcontaining Al and remaining in the reaction chamber was eliminatedbefore the growth of the active layer. Thereby, the problem of admixingof oxygen into the active layer together with Al was suppressed.

Further, the GaInP layer 161 of wide bandgap exists between the GaInNPlayer 162 and the GaInNAs active layer 143. Thus, degradation of theefficiency of optical emission, caused by the non-optical recombinationcenters in the GaInNP layer 162, is prevented.

With this, a GaInNAs surface-emission type semiconductor laser devicehaving a high efficiency of optical emission and oscillating with lowthreshold is formed by an MOCVD process, which is suitable for massproduction.

By using the surface-emission laser diodes of these embodiments incombination with the optical fibers as explained with FIGS. 21 and 22before, it becomes possible to form an optical transmission module oroptical transmission/reception module.

[Forty-Fifth Mode of Invention]

In a forty-fifth mode of the present invention, there is provided amethod of producing a semiconductor light-emitting device having asemiconductor layer containing Al between the substrate and the activelayer containing nitrogen, wherein there is provided a process ofsupplying a chloride compound gas into a growth chamber (reactionchamber) after growth of the semiconductor layer containing Al butbefore growth of the active layer containing nitrogen, as an etchinggas, such that an Al source or Al reactant or Al compound or Al isremoved from the growth chamber.

As noted above, the Al-containing residue becomes the cause ofincorporation of oxygen into the active layer containing nitrogen, whileoxygen in turn becomes the cause of non-optical recombination, Thus,after growth of the semiconductor layer containing Al but before thegrowth of the active layer containing Al, a gas that can remove theAl-containing residue remaining on the sidewall of the reaction chamber(growth chamber), the heating zone or the jig used for holding thesubstrate, is supplied to the growth chamber, and the incorporation ofoxygen into the active layer can be suppressed. The gas of chlorinesystem compound such as HCl has the effect of reacting with the reactantdeposits in the growth chamber and removes the same by etching. Thus,when a chlorine compound gas is supplied as etching gas after the growthof the semiconductor layer containing Al but before the growth of theactive layer containing nitrogen, the etching gas reacts with theAl-containing residue remaining on the reaction chamber sidewall, theheating zone, or the jig that holds the substrate, and the Al-containingresidue is removed. With this, it becomes possible to suppress theincorporation of oxygen into the active layer. A chlorine compound gas(HCl gas, for example) can be used in the form filled in a gas cylinder.In this case, a high purity gas containing little oxygen, water, and thelike, is preferable.

With this approach, it is possible to reduce the Al concentration in theactive layer containing nitrogen to 1×10¹⁹ cm⁻³ or less, and roomtemperature continuous oscillation has become possible. Furthermore, anoptical emission characteristics identical with the case in which theactive layer is formed on a semiconductor layer not containing Al wasobtained by reducing the Al concentration in the active layer containingnitrogen to 2×10¹⁹ cm⁻³ or less. Reference should be made to Table 4before.

Thus, in the present mode of the invention, a chlorine compound gas issupplied into the growth chamber as an etching gas after growing thesemiconductor layer containing Al but before starting the growth of theactive layer containing nitrogen in the process of producing asemiconductor light-emitting device having the semiconductor layercontaining Al between the substrate and the active layer containingnitrogen. The etching gas thereby removed the residual Al species suchas the Al source material, Al reactants, Al compound, or Al remaining inthe growth chamber. With this way, it is possible to suppress theincorporation of oxygen into the active layer and a semiconductorlight-emitting device having a high efficiency of optical emission canbe obtained.

[Forty-Sixth Mode of Invention]

According to a forty-sixth mode of the present invention for producing asemiconductor light-emitting device, the growth of the semiconductorlight-emitting device is interrupted in the process of producing thesemiconductor light-emitting device of the forty-fifth mode above whenconducting the process of removing the residual Al species such as theAl source material, Al reactants, Al compound, or Al that remaining inthe growth chamber. Further, the substrate of the semiconductorlight-emitting device is moved from the growth chamber to anotherchamber or taken out once from the growth chamber.

It should be noted that the chlorine compound gas has the effect ofetching the substrate in addition to the effect of removing the reactionproducts deposited in the growth chamber by causing an etching reaction.When conducting the process for removing the residual Al species such asthe Al source material, Al reactants, Al compound, or Al remaining inthe growth chamber, it is preferable that the substrate of thesemiconductor light-emitting device is not provided in the growthchamber. Of course, it is possible to that the growth is made thicker onthe substrate in advance by predicting the etching of the substrate. Inthis case, the growth process may be conducted continuously, withoutdisplacing the substrate.

[Forty-Seventh Mode of Invention]

In a forty-seventh mode of the present invention, there is formed aGaInP layer or GaPAs layer or GaInPAs layer in the first productionmethod of the semiconductor light-emitting device, after the process ofremoving the residual Al species such as the residual Al sourcematerial, Al reactant, Al compound or Al remaining in the growth chamberby the chlorine compound gas acting as an etching gas but before thegrowth of the active layer containing nitrogen.

It should be noted that the process of removing the residual Al speciessuch as the residual Al source material, Al reactant, Al compound or Alremaining in the growth chamber can be achieved by interrupting thegrowth of the semiconductor light-emitting device and moving thesubstrate of the semiconductor light-emitting device from the growthchamber to another chamber or taking out once from the growth chamber asnoted before. When the substrate is moved to another chamber, however,there is formed an oxide film on the surface of the epitaxial substrateas a result of moving the substrate to another chamber. Thus, when thisinterface is formed in the active region in which injection of thecarriers takes place, there is formed a non-optical recombination centerand the efficiency of optical emission is degraded at the time ofoperation of the light-emitting device.

When a material having a bandgap energy larger than the bandgap energyof the material forming the growth interruption surface, is grownbetween the growth interruption surface and the active layer containingnitrogen, the injection of carriers into the growth interruptioninterface is almost eliminated, and the degradation of efficiency ofoptical emission is prevented. When this growth interruption interfaceis analyzed by SIMS, oxygen, nitrogen or chlorine would be detected.From the point of the invention, a material not containing Al issuitable for the material that has the higher bandgap energy than thebandgap energy of the material grown at the time of the growthinterruption. For this purpose, it is possible to use a GaInP layer orGaPAs layer or GaInPAs layer. Of course, it is possible that thematerial contains other elements such as N or Sb. Further, thesematerial may achieve a lattice matching or may accumulate a strain,provided that the thickness is below a critical thickness. For example,an effect of compensating the strain of the active layer is achieved inthe case the active layer accumulates a compressional strain and whenthese materials have a tensile strain.

The semiconductor light-emitting device produced by any of the processof forty-fifth mode through forty-seventh mode can suppress theincorporation of oxygen into the active layer and can achieve a highefficiency of optical emission.

[Forty-Eighth Mode of Invention]

In a forty-eighth mode of the present invention, there is provided amethod of producing a surface-emission laser diode having an activeregion including at least one active layer containing nitrogen andproducing a laser light on a semiconductor substrate and upper and lowerreflectors provided above and below the active layer for producing thelaser light, and a cavity structure sandwiched between the upperreflector and the lower reflector, wherein the lower reflector has asemiconductor Bragg reflector in which the refractive index changesperiodically and reflecting incoming light by optical interference, thesemiconductor Bragg reflector having a low refractive index laser ofAlxGa1-xAs (0<x≦1) and a high refractive index layer of AlyGa1-yAs(0≦y<x≦1), characterized by the step of removing the residual Al speciessuch as the Al source, Al reactant, Al compound or Al remaining in thegrowth chamber by supplying a chlorine compound gas into the growthchamber as an etching gas, after growth of the lower reflectorcontaining Al but before growth of the active layer containing nitrogen.GaNAs, GaInNAs, InNAs, GaAsNSb, GaInNAsSb, and the like can be used forthe semiconductor layer containing nitrogen. Hereinafter, explanationwill be made for the example of GaInNAs. By adding N to GaInAs having alattice constant larger than that of GaAs, it becomes possible toachieve a lattice matching of GaInNAs to GaAs. Thereby, the bandgap isreduced. And optical emission in the 1.3 μm or 1.55 μm band becomepossible. Further, it becomes possible to use a widegap material ofAlGaAs or GaInP for the cladding layer, in view of the fact that thesematerials achieve lattice matching to the GaAs substrate.

Furthermore, with the addition of N, the bandgap is reduced as notedabove. Associated with this, the energy level of the conduction band andthe valence band is shifted in the lower energy side. As a result, theband discontinuity of the conduction band at the heterojunction isincreased remarkably. Thus, the temperature dependence of the laseroperation current is minimized.

Further, a surface-emission type semiconductor laser element isadvantageous for parallel transmission by two-dimensional integration,in view of the possibility of device miniaturization and low electricpower consumption. It has been difficult to obtain a practicalperformance in the conventional surface-emission type semiconductorlaser that uses the GaInPAs/InP system. By using the material of theGaInNAs system, it becomes possible to apply the Al Ga)As/(Al)GaAssemiconductor multilayer distributed Bragg reflector used successfullywith the 0.85 μm band surface-emission type semiconductor laser elementor the current-confinement structure formed by the selective oxidationof AlAs. Thus, it can be realized easily.

In order to realize this, improvement of crystal quality of the GaInNAsactive layer, decrease of resistance of the multilayer reflector, andimprovement of crystal quality and control of the multilayer filmstructure forming the surface-emission type semiconductor laser element,are important. In this 48th mode, a chlorine compound gas is suppliedinto the growth chamber after growing the lower part reflectorcontaining Al but before the growth of the active layer containingnitrogen so as to remove the residual Al species such as the Al sourcematerial, Al reactant, Al compound, or Al remaining in the growthchamber. Because of this, incorporation of oxygen, which forms thenon-optical recombination center, into the active layer containingnitrogen is suppressed, and it becomes possible to realize asurface-emission type semiconductor laser element having a lowresistance and driven by a low drive voltage, having a high efficiencyof optical emission and operating with a low threshold current, andfurther having excellent temperature characteristics. It should be notedthat the process of removing the residual Al species such as the Alsource material, Al reactant, Al compound, or Al remaining in the growthchamber is preferably conducted after moving the substrate to anotherchamber or taking out from the growth chamber.

[Forty-Ninth Mode of Invention]

According to the process of producing a surface-emission typesemiconductor laser element according to a forty-ninth mode of thepresent invention, a GaInP layer, or a GaPAs layer or a GaInPAs layer isprovided after the process of removing the residual Al species such asthe Al source material, Al reactant, Al compound, or Al remaining in thegrowth chamber with a chlorine compound gas acting as an etching gas butbefore the growth of the active layer containing nitrogen. Further, theremoval process by the etching gas is conducted during the growth of thesemiconductor distributed Bragg reflector.

When an etching removal process is provided during the growth of theactive region in which injection of carriers takes place, there is apossibility that the efficiency of optical emission is degraded due tothe non-optical recombination caused by oxidation, and the like. Bygrowing a GaInP layer or a GaPAs layer or a GaInPAs layer after theremoval of the residual Al species remaining in the growth chamber suchas the Al source material, Al reactant, Al compound or Al by using thechlorine compound etching gas but before the growth of the active layeras a part of the low refractive index layer of the reflector, it becomespossible to form an active region in the region closer to the activelayer than the GaInP layer or the GaPAs layer or the GaInPAs layer, byusing a narrow gap material (such as GaAs). Thereby, there is nodegradation of efficiency of optical emission, and the adversaryinfluence of the non-optical recombination center, formed in the regionwhere the removal process of the Al-containing residue has beenconducted, on the device performance is eliminated. Thus, it becomespossible to obtain a surface-emission type semiconductor laser elementoperating at low threshold current and having excellent temperaturecharacteristics.

[Fiftieth Mode of Invention]

In the production method of a surface-emission laser diode according toa fiftieth mode of the present invention, there is provided a GaInPlayer or a GaPAs layer or a GaInPAs layer in the production method ofthe surface-emission laser diode according to the forty-eighth mode ofthe present invention after the process of removing the residual Alspecies such as the Al source, Al reactant, Al compound or Al remainingin the growth chamber by the chlorine compound etching gas but beforethe growth of the active layer containing nitrogen, wherein the removalprocess by the etching gas is conducted while growing the cavitystructure. Here, the cavity structure means the region sandwiched by thelower reflector and the upper reflector.

The process of removing the residual Al species remaining in the growthchamber with the chlorine compound gas is conducted after growing thelower reflector containing Al but before growing the active layercontaining nitrogen. Also, this process may be conducted during thegrowth of the cavity. Yet, when the removal process is provided duringthe growth of the active region in which injection of carriers is made,there is a possibility that the efficiency of optical emission isdegraded because of the non-optical recombination caused by oxidation,and the like. On the other hand, when the growth is interrupted in thecavity part and the residual Al species remaining in the growth chamberby an etching gas (such as chlorine compound gas) and a GaInP layer or aGaPAs layer or a GaInPAs layer is grown before the growth of the activelayer, it becomes possible to form an active region closer to the activelayer than the GaInP layer or the GaPAs layer or the GaInPAs layer by anarrow gap material (such as GaAs). Thus, there is no problem ofdegradation of efficiency of optical emission even when the growth isinterrupted in the cavity, and it becomes possible to eliminate theadversary influence of the non-optical recombination center in theregion where removal of the residual Al species has been made on thedevice performance. Thereby, it becomes possible to obtain asurface-emission type semiconductor laser element operating at lowthreshold current and having excellent temperature characteristics.

Thus, it is possible to suppress the incorporation of oxygen, whichforms the non-optical recombination center, into the active layercontaining nitrogen in the semiconductor light-emitting device producedby the forty-eighth or fiftieth mode of the present invention. As aresult, a surface-emission type semiconductor laser element having a lowresistance and low drive voltage, high efficiency of optical emission,operating with low threshold current and excellent temperaturecharacteristics is obtained easily with low cost.

Further, it is possible to construct an optical transmission module oroptical transmission/reception module by using such a surface-emissiontype semiconductor laser element as the light source. By using asurface-emission type semiconductor laser element having low resistanceand low drive voltage, a low threshold current and excellent temperaturecharacteristics, it becomes possible to realize a low cost opticaltransmission module or optical transmission/reception module that doesnot require a cooling device.

Further, by using such an optical transmission module or opticaltransmission/reception module, an optical telecommunication system suchas low cost optical-fiber telecommunication system or low cost opticalinterconnection system can be realized.

<Embodiment 30>

FIGS. 100A and 100B are diagrams showing an example of the GaInNAssurface-emission laser diode according to Embodiment 30 of the presentinvention. It should be noted that FIG. 100B is an enlarged view of theactive region of FIG. 100A.

Referring to FIGS. 100A and 100B, the surface-emission typesemiconductor laser element of Embodiment 30 is constructed on a GaAssubstrate 301 having an (100) surface orientation and the size of 2inches and includes an n-type semiconductor distributed Bragg reflector302 that consists of a periodical structure in which an n-typeAlxGa1-xAs (x=0.9) layer and an n-type GaAs layer are stackedalternately 35 times with an optical thickness of 1/4 times theoscillation wavelength in each medium. On the lower reflector 302, thereis formed an undoped lower GaAs spacer layer 3310 and a multiple quantumwell active layer 3306 formed of three GaxIn1-xNyAs1-y (x, y) welllayers 3306 a and corresponding GaAs barrier layers 3306 b, and anundoped upper GaAs spacer layer 3311 is provided further thereon.

Further, a p-type semiconductor distributed Bragg reflector 3309 isformed on the undoped upper GaAs spacer layer 3311. The upper reflector3309 is formed a low refractive index layer 340 having an opticalthickness of 3λ/4 in which the AlAs selective oxidation layer 3309 issandwiched by a pair of AlGaAs layers (a C-doped p-type AlxGa1-xAs(x=0.9) layer having a thickness of λ/4–15 nm, a C-doped p-type AlAsselective oxidation layer having a thickness of 30 nm, a C-doped p-typeAlxGa1-xAs (x=0.9) layer having a thickness of 2/4–15 nm), a GaAs layerhaving the thickness of λ/4 (one period), and a periodical structure inwhich a C-doped p-type AlxGa1-xAs (x=0.9) and a p-type GaAs are repeatedalternately (for 25 times, for example), each with an optical thicknessof 1/4 the oscillation wavelength in each medium.

In FIG. 100A, the numeral 3312 represents the p side electrode, thenumeral 3313 represents the n side electrode, and the numeral 3314 is aninsulation film (polyimide).

Further, the GaAs layer 3309 a of the uppermost part of the upperreflector 3309 functions also as the contact layer for contact with theelectrode 3312. Further, the well layer 3306 a inside the active layer3306 was formed to have the In content x of 37% and the nitrogen contentof 0.5%. Further, the thickness of the well layer 3306 a was set to 7nm. The Well layer 3306 a thus formed had the compressional strain of2.5% (high strain) with respect to the GaAs substrate 3301.

For the MOCVD source of the GaInNAs active layer 3306, DMHy was used forthe source of nitrogen together with the source materials of TMG, TMIand AsH3. Further, H_ was used for the carrier gas. In view of the factthat DMHy decomposes at low temperature, DMHy is a material suited for alow temperature growth conducted at 600° C. or less. Thus, DMHy issuited particularly for the growth of the quantum well layer having alarge strain, which requires a low temperature growth process. In thecase the active layer 3306 accumulates a large strain as in the case ofthe GaInNAs surface-emission type semiconductor laser element ofEmbodiment 30, it is preferable to use a low temperature growth processthat achieves a non-equilibrium process. In this embodiment 30, theGaInNAs layer was grown at 540° C.

Also, in Embodiment 30, the growth was interrupted at the midway ofgrowth of the lower GaAs spacer layer 3310 at the location shown with abroken line in FIG. 100A so as to suppress the incorporation of oxygeninto the active layer 3306 and to avoid decrease of efficiency ofoptical emission. Further, the residual Al species are eliminated fromthe reaction chamber (growth chamber) by using the HCl gas, after movingthe substrate to another chamber. By supplying the HCl gas, the HCl gascauses an etching by reacting with the residual Al species remaining onthe sidewall of the reaction chamber (growth chamber) or the heatingbody or the jig that holds the substrate, and it is possible to suppressthe incorporation of oxygen into the active layer 3306. It is sufficientto conduct this process after the growth of the semiconductor layercontaining Al (the lower part reflector 3302 in the example of FIGS.100A and 100B) but before the growth of the active layer 3306 containingnitrogen.

In the production of the surface-emission type semiconductor laserelement of FIGS. 100A and 100B, the lower reflector 3302, the lowerspacer layer 3310, the active layer 3306, the upper spacer layer 3311,and the upper reflector 3309 are formed on substrate 301 consecutivelyand by exposing the sidewall of the p-type AlAs selective oxidizinglayer by forming a mesa structure having a predetermined size. Further,by oxidizing the sidewall of the AlAs layer thus exposed with watervapor, there is formed an AlxOy current confinement part 33092. Next,the etched part is filled polyimide 3314 for planarization, and thepolyimide on the upper reflector 3309 was removed from the p contactpart and the optical window part 3312 A. Further, a p-side electrode3312 is provided on the p-contact part excluding the optical window, andan n side electrode 3313 is provided on the rear side of the substrate3301.

The oscillation wavelength of the surface-emission type semiconductorlaser element thus produced was about 1.3 μm. Further, in Embodiment 30,it became possible to form the surface-emission semiconductor laserelement of long wavelength band on the GaAs substrate 3301 as a resultof use of GaInNAs for the active layer 3306. Also, in Embodiment 30,incorporation of oxygen into the active layer with Al is suppressed as aresult of removal of the Al species remaining in the apparatus by usingthe chlorine compound gas, such that the Al species remaining in theapparatus is not incorporated into the active layer together with oxygenat the time of growth of the active layer containing nitrogen. Withthis, it became possible to produce a GaInNAs surface-emission typesemiconductor laser element having a high efficiency of optical emissionand oscillating at low threshold by an MOCVD process, which is suitedfor mass production.

Further, because the current confinement is achieved by the selectiveoxidation of the selective oxidizing layer 33091 containing Al and As asthe primary components, the threshold current is reduced. According tothe current-confinement structure that uses the current confinementlayer formed of an Al oxide film formed by selective oxidation of theselective oxidizing layer, the current confinement layer is formedcloser to the active layer and spreading of the current is suppressedand it becomes possible to confine the carriers into a minute region notexposed to the atmosphere. As a result of oxidation that forms the Aloxide film, the refractive index becomes small and the light is confinedefficiently to the minute region in which the carriers are confined bythe convex lens effect. Thereby, the efficiency is improved remarkablyand the threshold current is reduced. Further, the production cost canbe reduced in view of the capability of forming the current-confinementstructure easily.

Conventionally, it was not possible to increase the supply rate of thesource material in view of the fact that an MBE process, which isinherently a growth process in a high vacuum environment, has been usedfor the production semiconductor layers such as GaInNAs containingnitrogen and other group V element. When the source supply rate isincreased, a large load is applied to the evacuation system. Thus, ahigh-power pump for a high-vacuum evacuation system has to be used,while the pump tends to cause a failure because of the need ofevacuating the residual source material inside the MBE chamber andbecause of the large load of the evacuation system. With this, thethroughput of production tends to be decreased.

More specifically, the surface-emission type semiconductor laser elementis constructed by sandwiching the active region containing at least oneactive layer that produces the laser by a pair of semiconductormultilayer reflectors. While the thickness of the crystal growth layeris about 3 μm in the case of an edge-emission laser diode, a thicknessexceeding 10 μm is needed in the 1.3 μm wavelength band surface-emissiontype semiconductor laser device. In the MBE process, which requires ahigh vacuum environment, however, the source material supply rate cannotbe increased. Thus, the growth rate is about 1 μm/h, at best. Thus, atleast the duration of 10 hours is needed for growing the thickness of 10μm, even in the case the growth interruption time for changing thesource supply rate is not counted.

Usually, the thickness of the active region is very small as comparedwith the whole device thickness (10% or less), and most part of thedevice is occupied by the layers forming the multilayer reflectors. In asemiconductor multilayer reflector, a low refractive index layer and ahigh refractive index layer are laminated alternately (for 20–40 times,for example), each with the optical thickness of 1/4 times theoscillation wavelength (thickness of λ/4). In the surface-emission typesemiconductor laser element formed on a GaAs substrate, the Al contentof the AlGaAs system material us changed to form the low refractiveindex layer (large Al content) and a high refractive index layer (smallAl content). In reality, however, the resistance is increasedparticularly at the p-side due to the effect of heterobarrier in each ofthe layers, and thus, an intermediate layer having the Al contentintermediate to the high refractive index layer and the low refractiveindex layer is interposed between the low refractive index layer and thehigh refractive index layer so as to reduce the resistance of themultilayer reflector. Thus, in the case of a surface-emission typesemiconductor laser element, not only it is necessary to grow thesemiconductor layers of different compositions over 100 layers but it isalso necessary to control the source supply rate instantaneously suchthat there is formed an intermediate layer between the low refractiveindex layer and the high refractive index layer of the multilayerreflector.

However, in the MBE process, the source supply rate is changed bychanging the temperature of the source cell and it is not possible tocontrol the composition as desired. Therefore, it is difficult to reducethe resistance in the semiconductor multilayer reflector grown by theMBE process, and the problem of high operating voltage cannot beavoided.

Contrary to this, the MOCVD process does not require high vacuum likethe MBE process and can control the composition by merely controllingthe source gas flow rate. Thus, it is possible to control thecomposition instantaneously and can achieve a large growth rate of 3μm/h or more, for example. Thus, the throughput is increased easily, andthe MOCVD process is thought to be a process most suitable for massproduction.

Thus, according to the present embodiment, a surface-emission typesemiconductor laser device of the 1.3 μm band of low electric powerconsumption is achieved with a low cost.

<Embodiment 31>

FIGS. 101A and 101B are diagrams showing the construction of a GaInNAssurface-emission type laser diode according to Embodiment 31 of thepresent invention. Further, FIG. 101B is an enlarged view of the activeregion of FIG. 101A. In FIGS. 101A and 101B, those parts correspondingto the parts described previously are designated by the same referencenumerals as in the case of FIGS. 100A and 100B.

The difference between Embodiment 31 and Embodiment 30 is that theprocess of removing the residual Al species such as the Al sourcematerial, Al reactant, Al compound, or Al remaining in the growthchamber is conducted during the growth of the lower reflector 3302. Itshould be noted that the low refractive index layer constituting thelower reflector 3302 is mostly formed of AlGaAs (more specifically thelower reflector 302 is formed mostly by the alternate stacking of theAlxGa1-xAs layer and the GaAs layer), wherein the single layer 3302 amost close to the active layer 3306 is formed of GaxIn1-xPyAs1-y (x=0.5,y=1, for example), and the growth interruption is made during the growthof the underlying high refractive index layer of GaAs. Thereby, thegrowth substrate is moved to another chamber and the HCl gas is suppliedto the reaction chamber (growth chamber) for removal of theAl-containing residues in the reaction chamber.

The oscillation wavelength of the surface-emission type semiconductorlaser element thus produced was about 1.3 μm. Also, because of the useof GaInNAs to the active layer, it became possible to form thesurface-emission type semiconductor laser element of the long wavelengthband on a GaAs substrate.

Also, because HCl is supplied after growing the semiconductor layercontaining Al but before the growth of the active layer containingnitrogen as an etching gas so that the residual Al-containing compoundsremaining in the apparatus are not incorporated into the film at thetime of growth of the active layer with oxygen, the residual Al speciesremaining in the reaction chamber (growth chamber) is removed before thegrowth of the active layer, and incorporation of oxygen into the activelayer together with oxygen is suppressed. Yet, there is a possibilitythat an oxide film is formed at the growth interruption interface as aresult of interruption of the growth, and there is a possibility ofoccurrence of defects. In this way, there is a possibility thatnon-optical recombination centers are formed.

However, because the GaInPAs layer 3302 a of a wide bandgap material isinserted between the growth interruption interface and the GaInNAsactive layer 3306 in the present embodiment, injection of the carriersinto the growth interruption interface is eliminated positively, anddegradation of efficiency of optical emission by the non-opticalrecombination centers at the growth interruption interface iseliminated. In the present embodiment, the GaInPAs layer has a latticematching composition. Thus, it has the effect of compensating the strainof the active layer 3306, in the case the active layer 3306 has a highcompressional strain composition like this second embodiment, providedthat the GaInPAs layer 3302 a has a tensile strain composition. Thereby,an advantageous effect of suppressing the lattice relaxation of theactive layer 3306 is achieved. In this way, a GaInNAs surface-emissiontype semiconductor laser element having a high efficiency of opticalemission and oscillating with low threshold was produced by an MOCVDprocess suitable for mass production.

<Embodiment 32>

FIGS. 102A and 102B are diagrams showing the construction of a GaInNAssurface-emission type laser diode of Embodiment 32 of the presentinvention. Further, FIG. 102B is an enlarged view of the active regionof FIG. 102A. In FIGS. 102A and 102B, those parts corresponding to theparts of FIGS. 101A, 101B and FIGS. 100A and 100B are designated by thesame reference numerals and the description thereof will be omitted.

The difference between the present embodiment and that of Embodiment 31exists in the point that the process of removing the residual Al speciesremaining in the growth chamber is conducted during the growth of theGaxIn1-xPyAs1-y layer 302 a (x=0.5, y=1, for example) constituting thelow refractive index layer of the lower part reflector 302, wherein thegrowth of the GaInPAs layer 302 a is interrupted and halfway and an HClgas is supplied to the reaction chamber (growth chamber) after movingthe growth substrate to another chamber for and eliminating theAl-containing residue.

The oscillation wavelength of the surface-emission semiconductor laserelement thus produced was about 1.3 μm. Also, it became possible to forma surface-emission type semiconductor laser element of long wavelengthband on a GaAs substrate as a result of use of GaInNAs for the activelayer.

Further, in order that the compound containing Al and not remaining inthe apparatus is incorporated into the film together with oxygen at thetime of growth of the active layer containing nitrogen, HCl was suppliedas an etching gas so as to remove the compound containing Al andremaining in the apparatus. With this, admixing of oxygen the activelayer together with Al was suppressed. Furthermore, in this thirdembodiment, the degradation of efficiency of optical emission by thenon-optical recombination center is prevented because of the existenceof the GaInPAs layer 302 a of wide bandgap between the growthinterruption interface and the GaInNAs active layer.

With this, a GaInNAs surface-emission type semiconductor laser elementof high efficiency of optical emission and low threshold of oscillationwas produced by an MOCVD process suitable for mass production.

<Embodiment 33>

FIGS. 103A and 103B are diagrams showing the constitutional example of aGaInNAs surface-emission type semiconductor laser element of Embodiment33 of the present invention. Further, FIG. 103B is an enlarged view ofthe active region of FIG. 103A. In FIGS. 103A and 103, those partssimilar to the parts of FIGS. 100A and 100B and FIGS. 102A and 102B aredesignated by the same reference numerals.

The difference of the present embodiment over Embodiment 32 exists inthe point that the process of removing the residual Al species remainingin the growth chamber is conducted during the growth of the GaPAs layer320 formed for the cavity part, and the growth of the GaPAs layer 3320is interrupted halfway. Thereby, the growth substrate is moved toanother chamber and an HCl gas is supplied to the reaction chamber(growth chamber) for eliminating the residual Al species.

More specifically, in the present embodiment, a GaPAs layer 3320 isformed on the AlGaAs low refractive index layer 3302 a at the upper partmost of the lower reflector 3302, and the residual Al species wereremoved during the halfway of growth of the GaPAs layer 3320. Further,it is possible to form a GaAs layer is between the AlGaAs low refractiveindex layer 3302 a and the GaPAs layer 3320 and eliminate theAl-containing residue halfway of the growth of the GaAs layer.

The oscillation wavelength of the surface-emission type semiconductorlaser element thus produced was about 1.3 μm. Further, asurface-emission type semiconductor laser element of long wavelengthband was formed on a GaAs substrate as a result of use of GaInNAs forthe active layer.

Also, HCl is supplied as an etching gas between the semiconductor layercontaining Al and the with the active layer containing nitrogen, suchthat the compound containing Al and remaining in the apparatus is notincorporated into the film together with oxygen at the time of growth ofthe active layer containing nitrogen. Therefore, the compound containingAl and remaining in the reaction chamber (growth chamber) was removedbefore growing the active layer. With this, admixing of oxygen to theactive layer with Al was suppressed. On the other hand, there is apossibility that an oxide film is formed at the growth interruptionsurface as a result of interruption of growth and defects may be caused.With this, there is a possibility that a non-optical recombinationcenter is formed.

However, the GaPAs layer 3320 having a wider bandgap than the GaAsspacer layer is inserted between the growth interruption interface andthe GaInNAs active layer 3306 in the present embodiment. Because ofthis, injection of carriers into the growth interruption interface issuppressed, and degradation of efficiency of optical emission by thenon-optical recombination centers at the growth interruption interfaceis positively prevented. It should be noted further that the GaPAs layer3320 has a tensile strain with respect to the GaAs substrate 3301. Inthe case the active layer 3306 has a composition providing a highcompressional strain as in the case of the present embodiment, the GaPAslayer 3320 having a tensile strain has an advantageous effect ofcompensating for the strain of the active layer 3306, and it becomespossible to suppress the lattice relaxation of the active layer 3306.Although the GaPAs layer 3320 is provided in the present embodiment, itis possible to provide a GaInP layer or a GaInPAs layer in placethereof.

With this, it becomes possible to produce the GaInNAs surface-emissiontype semiconductor laser element, having a high efficiency of opticalemission and oscillating with low threshold by an MOCVD process suitablefor mass production.

[Fifty-First Mode of Invention]

It is possible to form an optical transmission module of FIG. 21 or anoptical transmission/reception module of FIG. 22 explained withpreviously, by combining the surface-emission type semiconductor laserelement of various modes and embodiments of the present inventionexplained before with an optical fiber.

In these optical transmission modules or optical transmission/receptionmodules, the laser beam from the GaInNAs surface-emission typesemiconductor laser element of the 1.3 μm band is injected into a quartzoptical fiber for transmission. In this case, by arranging a pluralityof surface-emission type semiconductor laser elements of differentoscillation wavelengths in the form of a one-dimensional ortwo-dimensional array, it becomes possible to increase the transmissionrate by way of wavelength multiplex transmission. Also, by arranging thesurface-emission type semiconductor laser element in the form ofone-dimensional or two-dimensional array, and by coupling an opticalfiber bundle consisting of a plurality of optical fibers incorrespondence to each of the optical fibers, it becomes possible toincrease the transmission speed. Further, it becomes possible to realizea highly reliable optical telecommunication system of low cost, inaddition to a highly reliable optical transmission module of low cost,by using the surface-emission type semiconductor laser element of thepresent invention for the optical telecommunication system. Also, itbecomes possible to realize a system generating little heat and can beused up to high temperature without cooling, in view of the fact thatthe surface-emission type semiconductor laser element using GaInNAs hasexcellent temperature characteristics and low threshold.

Particularly, by combining a fluorine-added POF (plastics opticalfiber), which provides a low loss at long wavelength band such as 1.3 μmwith a surface emission laser diode that uses GaInNAs for the activelayer, it becomes possible to realize an extremely low cost module inview of the fact that the optical fiber itself is low cost and in viewof the fact that the diameter of the optical fiber is large and the costof mounting is reduced because of the easiness of coupling with theoptical fiber.

The optical telecommunication system that uses the surface-emissionlaser element of the present invention can be used not only for a longdistance telecommunication using an optical fiber but also for a shortdistance telecommunication such as transmission between apparatuses suchas computers as in the case of LAN, transmission between circuit boards,transmission between LSIs on a board, or transmission inside an LSI.

Although the processing performance of LSIs has been improved in recentyears, there is a bottleneck problem of transfer rate for the partconnecting the LSIs. In the case that the signal connection inside thesystem is changed to an optical interconnection from a conventionalelectric interconnection, for example, it becomes possible to realize asuper-fast computer system by using the optical transmission module oroptical transceiver module of the present invention for theinterconnection between the circuit boards inside the computer system orfor the interconnection between the LSIs on a circuit board or for theinterconnection of between the elements in an LSI.

Also, it is possible to construct a ultrahigh speed network system byconnecting plural computer systems and the like, by using the opticaltransmission module and or optical transmission/reception module of thepresent invention. Especially, a surface-emission type semiconductorlaser element is suited for an optical telecommunication system ofparallel-transmission type in view of remarkable low electric powerconsumption as compared with an edge-emission laser diode and in view ofeasiness of construction a two-dimension array.

As explained above, by using the GaInNAs system, which is asemiconductor layer containing nitrogen, it becomes possible to use amultilayer distributed Bragg semiconductor reflector ofAl(Ga)As/(Al)GaAs system and a current confinement structure formed byselective oxidation of AlAs, which have been used successfully with a0.85 μm band surface-emission type semiconductor laser element that usesa GaAs substrate. By producing a surface-emission type semiconductorlaser element according to the process of the present invention, thecrystal quality of the GaInNAs active layer is improved and theresistance of the multilayer reflector is reduced. Further, the qualityand controllability of the multilayer structure forming thesurface-emission laser element are improved. As a result, apractical-level, high-performance long wavelength band surface-emissiontype semiconductor laser element of the 1.3 μm band is realized. Byusing these elements, it becomes possible to realize an opticaltelecommunication system such as an optical fiber telecommunicationsystem or an optical interconnection system of a low cost that does notrequire a cooling device.

Further, the present invention is by no means limited to the embodimentsdescribed heretofore, but various variations and modifications may bemade without departing from the scope of the invention.

1. A semiconductor light-emitting device, comprising: a substrate; an active layer containing nitrogen; and a semiconductor layer containing Al interposed between said substrate and said active layer, wherein an impurity element that forms a non-optical recombination level in said active layer is included in the active layer in a concentration at which said semiconductor light-emitting device can achieve continuous laser oscillation at room temperature.
 2. A semiconductor light-emitting device as claimed in claim 1, wherein there is provided an intermediate layer between said semiconductor layer and said active layer, and wherein said impurity concentration of said active layer is equal to or smaller than an impurity concentration level of said impurity element in said intermediate layer.
 3. A semiconductor light-emitting device, comprising: a substrate; an active layer containing nitrogen; and a semiconductor layer containing Al provided between said substrate and said active layer, wherein a concentration of oxygen in said active layer is such that said semiconductor light-emitting device can achieve continuous laser oscillation at room temperature.
 4. A semiconductor light-emitting device as claimed in claim 3, wherein there is provided an intermediate layer between said semiconductor layer and said active layer, said oxygen concentration in said active layer being equal to or smaller than an oxygen concentration level of said intermediate layer.
 5. A semiconductor light-emitting device, comprising: a substrate; an active layer containing therein nitrogen; and a semiconductor layer containing therein Al provided between said substrate and said active layer, wherein an oxygen concentration of said active layer is less than 1.5×10¹⁸ cm⁻³.
 6. A semiconductor light-emitting device as claimed in claim 5, wherein there is provided an intermediate layer between said semiconductor layer and said active layer, said oxygen concentration of said active layer is 3×10¹⁷ cm⁻³ or less.
 7. A semiconductor light-emitting device, comprising: a substrate; an active layer containing nitrogen; and a semiconductor layer containing Al provided between said substrate and said active layer, wherein an Al concentration of said active layer is such that said semiconductor light-emitting device can achieve continuous laser oscillation at room temperature.
 8. A semiconductor light-emitting device as claimed in claim 7, wherein there is provided an intermediate layer between said semiconductor layer and said active layer, said concentration of Al in said active layer is equal to or smaller than a concentration level of Al of said intermediate layer.
 9. A semiconductor light-emitting device, comprising: a substrate; an active layer containing nitrogen; a semiconductor layer containing Al provided between said substrate and said active layer, wherein said active layer contains Al with a concentration of less than 2×10¹⁹ cm⁻³.
 10. A semiconductor light-emitting device as claimed in claim 9, wherein there is provided an intermediate layer between said semiconductor layer and said active layer, said concentration of Al contained in said active layer is 1.5×10¹⁸ cm⁻³ or less.
 11. A semiconductor light-emitting device having a substrate, an active layer containing nitrogen and a semiconductor layer containing Al provided between said substrate and said active layer, wherein there is provided a semiconductor layer containing nitrogen between said semiconductor layer containing Al and said active layer containing nitrogen, said semiconductor layer containing Al constituting a distributed Bragg reflector, said semiconductor light-emitting device being a surface-emission type laser diode device emitting an optical beam perpendicularly to a substrate surface.
 12. A semiconductor light-emitting device comprising a substrate, an active layer containing nitrogen and a semiconductor layer containing Al between said substrate and said active layer containing nitrogen, wherein there is formed a semiconductor layer containing nitrogen between said semiconductor layer containing Al and said active layer containing nitrogen; said semiconductor layer containing Al constituting a distributed Bragg reflector, said semiconductor light-emitting device being a surface-emission type laser diode device emitting an optical beam perpendicularly to a substrate surface. 